Patent Publication Number: US-7217110-B2

Title: Compact rotary compressor with carbon dioxide as working fluid

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a rotary compressor having a compact design wherein the compression chamber is defined by the rotor of the motor driving the compressor. 
   2. Description of the Related Art 
   Rotary compressors typically include a housing in which a motor and a compression mechanism are mounted on a drive shaft. Rotary type compression mechanisms typically include a roller disposed about an eccentric portion of the shaft. The roller is located in a cylinder block that defines a cylindrical compression space or chamber. At least one vane extends between the roller and the outer wall of the compression chamber to divide the compression chamber into a suction pocket and a compression pocket. The roller is eccentrically located within the compression chamber. As the shaft rotates, the suction pocket becomes progressively larger, thereby drawing a refrigerant or other fluid into the suction pocket. Also as the shaft rotates, the compression pocket becomes progressively smaller, thereby compressing the fluid disposed therein. Oftentimes the vane is biased into contact with either the wall of the compression chamber or the roller by a spring. Other configurations of rotary compressors are also known. 
   SUMMARY OF THE INVENTION 
   The present invention provides a compact rotary compressor where the compression chamber is located within the rotor and the roller is mounted on a stationary shaft and wherein the shaft has a longitudinal passage defining the refrigerant inlet and an oil passage that is in communication both with the refrigerant inlet passage in the shaft and an oil sump contained within the compressor housing. The interior of the compressor housing is at discharge pressure whereby oil from the sump enters the oil passage in the shaft and flows upwardly through the stationary shaft due to the pressure differential within the stationary shaft. At least a portion of the oil exits the stationary shaft through the same radial passage as does the refrigerant. 
   The present invention comprises, in one form thereof, a rotary compressor for compressing a working fluid including a housing having an oil sump. A stationary shaft extends into the housing and includes a longitudinal passage. The longitudinal passage has an oil inlet in fluid communication with the oil sump. A working fluid inlet receives the working fluid. A motor has a stator and a rotor. The rotor is rotatably mounted on the shaft within the housing and includes an internal compression chamber in fluid communication with the longitudinal passage. A roller is rotatably mounted on the shaft and eccentrically disposed within the compression chamber. The roller is coupled to the rotor such that rotation of rotor compresses the working fluid within the compression chamber. 
   The housing may include an interior chamber in which the oil sump is disposed. The motor may increase a pressure within the interior chamber to thereby cause oil from the oil sump to enter the oil inlet and flow within the longitudinal passage in a substantially upward direction. 
   The shaft may include at least one substantially radially-oriented passage providing fluid communication between the longitudinal passage and the compression chamber. At least a portion of the oil and at least a portion of the working fluid may exit the longitudinal passage through a same one of the radially-oriented passages. 
   The compressor may also include a bearing disposed between the shaft and the roller. The radially-oriented passage may allow the oil from the longitudinal passage to reach the bearing. 
   The housing may include an outlet to allow compressed working fluid to exit the interior chamber. The roller may include a channel providing fluid communication between the longitudinal passage and the compression chamber. 
   The rotor may be a non-laminated integrally formed part and may include a radially outer surface having a plurality of magnets mounted therein. The rotor may also include a vane extending radially inwardly within the compression chamber and coupling the rotor to the roller. Further, the roller may define a recess having a bushing mounted therein, wherein the bushing defines a radially extending slot with the vane being disposed within the slot. Because the bushing is mounted on an eccentric roller, the bushing is slidable relative to the vane. 
   The roller and the vane may divide the compression chamber into a variable-volume suction pocket and a variable-volume compression pocket. The rotor and the roller may rotate and thereby compress working fluid in the compression pocket and draw working fluid into a the suction pocket. 
   The compressor may also include first and second end plates disposed at opposite axial ends of the compression chamber. At least one of the end plates may define a fluid passageway providing fluid communication between the internal passageway of the shaft and the compression chamber. The shaft extends through one or both of the end plates. The stator circumscribes the rotor, the compression chamber disposed therein and the first and second end plates. 
   One of the end plates disposed at an end of the compression chamber may have a discharge valve cavity in fluid communication with the compression chamber and a discharge valve member disposed within the discharge valve cavity and controlling fluid flow from the compression chamber through the discharge valve cavity. 
   The present invention comprises, in another form thereof, a rotary compressor for compressing a working fluid including a stationary shaft having a longitudinal passage with a lubricant inlet and a working fluid inlet to receive the working fluid. A motor has a stator and a rotor. The rotor is rotatably mounted on the shaft and includes an internal compression chamber. A roller is rotatably mounted on the shaft and within the compression chamber wherein the roller is rotatable about an axis spaced from a rotational axis of the rotor. The compression chamber is divided between the roller and the rotor into a variable-volume suction pocket and a variable-volume compression pocket. The compression pocket is at least periodically in fluid communication with a chamber containing a lubricant source wherein compressed working fluid is communicated to the chamber. The suction pocket is at least periodically in fluid communication with the longitudinal passage wherein working fluid is communicated from the longitudinal passage to the suction pocket. The roller is coupled to the rotor and is eccentrically mounted within the compression chamber such that rotation of the rotor shrinks the compression pocket and expands the suction pocket. The expansion of the suction pocket operates to draw the working fluid through the longitudinal passage and into the suction pocket. The shrinkage of the compression pocket operates to compress the working fluid within the compression pocket. Lubricant from the lubricant source is forced through the lubricant inlet and into the longitudinal passage due to a pressure differential created by the operation of the rotary compressor. 
   The present invention comprises, in yet another form thereof, a rotary compressor for compressing a working fluid including a housing having an interior chamber and an oil sump disposed within the interior chamber. A stationary shaft extends into the interior chamber and includes a longitudinal passage. The longitudinal passage has an oil inlet in fluid communication with the oil sump and a working fluid inlet to receive the working fluid. A motor includes a stator and a rotor. The rotor is rotatably mounted on the shaft within the interior chamber and has an internal compression chamber in at least periodic fluid communication with the longitudinal passage and in at least periodic fluid communication with the interior chamber. The rotor rotates and thereby draws the working fluid from the longitudinal passage into the compression chamber. The rotor rotation also increases pressure in the interior chamber such that oil from the oil sump enters the oil inlet and flows within the longitudinal passage in a substantially upward direction. 
   The invention comprises, in still another form thereof, a rotary compressor assembly that includes a motor having a rotor defining a substantially cylindrical compression chamber having an axis, a first plate and a second plate fixed relative to the rotor and defining opposite ends of the compression chamber and a stationary shaft extending axially through the compression chamber. A roller is rotatably mounted on the stationary shaft and disposed within the compression chamber. A vane is provided and has an outer radial end fixed to the rotor. The vane extends radially inwardly and is fixed to the first and second plates proximate a radial inner end of the vane. The roller defines a slot and the radial inner end of the vane is disposed within the slot wherein the vane and slot are relatively slidable. Rotation of the rotor rotates the first and second plates and the vane while rotation of the vane drivingly rotates the roller. A pin may be used to fix the vane to the first and second plates. The pin extends through the vane proximate the inner radial end of the vane and at least partially engages the first and second plates. 
   An advantage of the present invention is that oil can be provided to a bearing and other moving parts during operation. The oil can be supplied under pressure that is created by the compressor. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above mentioned and other features and objects of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein: 
       FIG. 1  is a side sectional view of a compact rotary compressor in accordance with the present invention. 
       FIG. 2  is another side sectional view, from another angle, of the compressor of  FIG. 1 . 
       FIG. 3  is a top sectional view of the compressor of  FIG. 1  along line  3 — 3  showing a first position. 
       FIG. 4  is a top sectional view of the compressor of  FIG. 1  showing a second position. 
       FIG. 5  is a perspective view of the roller of the compressor of  FIG. 1 . 
       FIG. 6  is a top view of the roller of  FIG. 5 . 
       FIG. 7  is sectional view of the roller along line  7 — 7  in  FIG. 6 . 
       FIG. 8  is a side sectional view of the stationary shaft of the compressor of  FIG. 1 . 
   

   Corresponding reference characters indicate corresponding parts throughout the several views. Although the exemplification set out herein illustrates an embodiment of the invention, in one form, the embodiment disclosed below is not intended to be exhaustive or to be construed as limiting the scope of the invention to the precise form disclosed. 
   DESCRIPTION OF THE PRESENT INVENTION 
   Referring now to the drawings and particularly to  FIGS. 1 and 2 , there is shown a compact rotary compressor  10 . Compressor  10  has hermetically sealed housing  12  including base  14 , annular side wall  15  and top wall  16 . Base  14  is hermetically sealed to wall  15  by welding, brazing, or the like at location  17 . Similarly, side wall  15  is hermetically sealed to top wall  16  by welding, brazing, or the like at location  18 . The diameter of base  14  is greater than the diameter of annular side wall  15  to provide a flange  20  that may have throughholes (not shown) therein for mounting compressor  10 . 
   Compressor  10  includes electric motor  24  having stator  26  and rotor  28  which defines a portion of compression mechanism  30  provided for compressing refrigerant, such as carbon dioxide, from a low pressure to a higher pressure for use in a refrigeration system, for example. Stator  26 , having coil assembly  32 , is rigidly mounted and circumscribes rotor  28 . Extending through rotor  28  is stationary shaft  34  which can be integrally formed at upper end  36  with top wall  16 . An aperture  38  may be centrally formed in top wall  16  for receiving a tube or fitting  39  that can be fixedly attached to top wall  16  by welding, brazing, or the like. Suction pressure refrigerant can enter longitudinal passage  126  via fitting  39 . In the illustrated embodiment, weld  40  secures fitting  39  to top wall  16 . 
   Referring to  FIGS. 3 and 4 , a plurality of pockets  41  are formed in the outer circumferential surface of rotor  28  in which permanent magnets  42 , such as neodymium iron boron magnets, are mounted by any suitable method including the use of adhesives, for example. Rotor  28  is circumscribed by lamination stack  44  of stator  26  ( FIG. 1 ) and, during operation of compressor  10 , stator  26  generates a rotating electromagnetic field to rotationally drive rotor  28  having permanent magnets  42  mounted thereon. Rotor  28  also defines an internal compression chamber  52 . In the illustrated embodiment, rotor  28  is integrally formed from a solid metal material such as steel, powder metal, ductile iron, or the like in the general shape of an annular ring. The rotor may be manufactured using any suitable method including electric discharge machining (EDM). By using a solid integral part to form rotor  28 , no lining is required for internal compression chamber  52 . A vane  54  extends radially inwardly within compression chamber  52  to engage roller  50  as discussed in greater detail below. 
   Stationary shaft  34  and integral top wall  16  can be formed from any suitable metal material including steel, powder metal, ductile iron, or the like by any conventional method including machining, for example. Referring to  FIG. 1 , an eccentric portion  48  is integrally formed on shaft  34  and is located within compression chamber  52  defined by rotor  28 . Roller  50  forms a part of compression mechanism  30  and is rotatably mounted on eccentric  48 . Referring to  FIGS. 3 and 4 , vane  54  is snugly received in a slot  55  that can be machined in the inner surface of rotor  28  that defines compression chamber  52 . Alternatively, vane  54  can be integrally formed with rotor  28 . Vane  54  extends radially inwardly from the inner surface of rotor  28  and engages roller  50 . Vane  54 , together with roller  50  divides compression chamber  52  into a variable-volume, crescent-shaped suction pocket  56   a  and a variable-volume, crescent-shaped compression pocket  56   b.    
   Referring to  FIGS. 3 and 4 , in order to allow for the relative sliding movement between vane  54  which extends radially inwardly from cylinder block portion  46  of rotor  28  and roller  50 , roller  50  is provided with cylindrical aperture  58 , as best seen in  FIGS. 5 ,  6  and  7 . Aperture  58  extends longitudinally through roller  50  adjacent the outer periphery thereof and defines an opening in an outer circumferential surface  59  of roller  50 . Guide bushing  60  is mounted in aperture  58  and has a longitudinally extending slot  62  formed therein to slidably receive vane  54  such that as rotor  28  together with fixed vane  54  and roller  50  rotate, the surfaces of the bushing  60  facing vane  54  slide along vane  54  due to the roller/rotor eccentricity and roller  50  moves toward and away from the compression chamber wall adjacent vane  54 . Bushing  60  also oscillates within aperture  58  to allow for change in angular position of vane  54  with respect to aperture  58  as rotor  24  and roller  50  are rotated. Similarly, aperture  58  has a radially outer opening that provides a sufficiently large operating clearance to allow for this relative angular movement of vane  54  during operation of the compressor. In the illustrated embodiment, bushing  60  is a two-piece bushing, however, alternative embodiments may employ a single piece bushing wherein an interconnecting web of material extends between the two halves of the bushing through a portion of space  130  and is sufficiently thin to avoid interfering with the inner radial end of vane  54  and the reciprocation of vane  54  within slot  62 . 
   Guide bushing  60  can be made from a material with suitable antifriction properties. In the illustrated embodiment, bushing  60  is formed using Vespel SP-21, a material commercially available from E.I. du Pont de Nemours and Company, and which facilitates the reduction of frictional losses caused by sliding movement of vane  54  relative to slot  62  and relative oscillating movement of bushing  60  within aperture  58  of roller  50 . The use of a guide bushing  60  from a material with good antifriction properties facilitates the reduction of wear of the surfaces of roller  50 , vane  54 , and guide bushing  60  that are in moving contact to thereby improve the longevity and reliability of the compressor. 
   As discussed above, and in more detail below, vane  54  can be snugly fixed within slot  55  or perhaps integrally formed with the cylinder block portion  46  of rotor  28  such that vane  54  does not move relative to rotor  28 . The use of bushing  60  together with such a fixed vane eliminates the need for a vane spring to press the vane against the roller. The use of bushing  60  to slidably receive vane  54 , instead of a spring biased vane, may also reduce the frictional losses created by the vane during operation of the compressor. The relatively minimal frictional losses caused by vane  54  facilitates the minimization of power losses due to friction. The use of a fixed vane that is slidably received within bushing  60  also facilitates the reduction of refrigerant vapor leakage across the barrier formed by vane  54  between a relatively high pressure compression pocket  56   b  to a relatively low pressure suction pocket  56   a  during operation of the compressor. The reduced frictional losses and refrigerant leakage facilitate the efficient and reliable operation of the compressor. 
   Referring to  FIG. 1 , compression mechanism  30  also includes a disk-shaped top end plate  70  located in adjacent contact with upper axial end surface  66  of rotor  28  to partially define and seal compression chamber  52 . Top plate  70  is provided with central aperture  68  through which shaft  34  extends. A disk-shaped bottom end plate  74  is positioned in adjacent contact with the lower axial end surface  76  of rotor  28  and partially defines and seals compression chamber  52 . Bottom plate  74  is provided with central aperture  64  through which a lower, non-eccentric portion  78  of shaft  34  extends. Non-eccentric portion  78  has a smaller diameter than eccentric portion  48 , which has a smaller diameter than upper portion  36 . Bottom end plate  74  is rotatably mounted on stationary shaft  34  via a sleeve-like self-lubricated bearing  88  that is received in aperture  64 . A metal washer  72  may be provided, bearing against a polyamide thrust member  89 . Similarly, on the opposite end of shaft  34 , a metal washer  96  may bear against a polyamide thrust member  92 . In order to anchor compression mechanism  30  in adjusted position on shaft  34 , a distal tip  80  of non-eccentric portion  78  may be threaded, as indicated by dashed lines  81  in  FIG. 8 , to receive a holding nut  82 . A spring washer  90  can be used as a preload spring for thrust surfaces  89 ,  92  and to improve axial positioning of compression mechanism  30  on shaft  34  with limited or no axial play. 
   Upper end plate  70 , rotor  28  and lower plate  74  can be secured together to define compression chamber  52 . In the illustrated embodiment, a plurality of bolts  22  extend through apertures in upper end plate  70 , rotor  28 , and lower end plate  74  to secure these components to one another. Alternative embodiments may employ alternative methods of securing these components together such as welding. 
   Compression assembly  30  can be rotatably mounted on shaft  34  by flanged, self-lubricated bearings  84 ,  88  and a needle roller and cage radial assembly bearing  86  which are press-fit into the apertures defined by upper end plate  70 , lower end plate  74 , and the inner diameter of roller  50 , respectively. Bearing  86  can be axially guided by a shoulder  94  machined at one end in roller  50  and a shaft shoulder  95  on the other (upper) end of bearing  86 . In one embodiment, the height of bearing  86  may be approximately between 70% and 90% of the diameter of bearing  86  in order to provide improved axial guidance. When the compressor is operating and rotor  28  is rotated, bearings  84 ,  86 , and  88  rotatably support compression assembly  30  as it is rotatably driven about stationary shaft  34 . 
   As best seen in  FIG. 1 , bearings  84  and  88  which rotatably support rotor  28  and the first and second end plates enclosing compression chamber  52  are centered on rotor axis  24   a , and bearing  86  rotatably supporting roller  50  is centered on roller axis  50   a  defined by eccentric portion  48  of shaft  34 . Axes  24   a  and  50   a  are spaced apart whereby roller  50  forms a line, or area, of contact with the inner surface of rotor  28  that defines compression chamber  52 . The line or area of contact is fixed relative to shaft  34 , but progressively travels along the circumference of the inner surface of rotor  28  as rotor  28  and roller  50  rotate in a clockwise direction indicated by arrow  102  about their respective axes. The relative rotation of rotor  28  and compression chamber  52  and roller  50  with respect to shaft  34  and axes  24   a  and  50   a  defines suction pocket  56   a  ( FIG. 4 ) for drawing refrigerant into compression chamber  52  which then becomes a compression pocket  56   b  for compressing refrigerant therein as rotor  28  continues to rotate. 
   Bearings  84 ,  86 ,  88  and thrust members  89 ,  92  may be formed from a polyamide material having relatively low coefficients of static and kinetic friction such as Vespel SP-21. Another beneficial characteristic associated with polyamide is that it demonstrates thermal stability over a relatively broad temperature range. For example, polyamide bushings may be capable of withstanding a bearing pressure of approximately 300,000 lb ft/in 2  and a contact temperature of 740° F. For improved performance of the bushings and to avoid overheating, bushings  84 ,  86  and  88  advantageously may have a length-to-inside diameter ratio of equal to or less than 3:2. 
   Compressor  10  as described above utilizes a bushing  60  and bearings  84  and  88  that may potentially operate without lubrication. However, as discussed in more detail below, compressor  10  includes an oil sump from which lubricating oil is delivered to bearing  86  which may be in the form of a needle or ball-type bearing that requires lubrication. Lubricating oil may also be provided to bearing  88  and bushing  60  from the oil sump. 
   In the illustrated embodiment, shaft  34  includes a longitudinal passage  126  having a refrigerant inlet  104 , best shown in  FIG. 8 , at an upper end of shaft  34  and an oil inlet  108  at a lower end of shaft  34 . Longitudinal passage  126  is in fluid communication with compression chamber  52  via a radially-oriented passage or channel  124  and a through channel  114  in roller  50 . Channel  114  extends between an annular inner surface  116  ( FIG. 5 ) of roller  50  and outer surface  59 . An annular groove  122  is disposed at the outermost end of radial passage  124  on shaft  34 . Once the refrigerant gas is compressed to a higher pressure within compression pocket  56   b , the compressed gas is discharged through a discharge passage  120  ( FIG. 1 ) and an integral discharge valve  118  into an interior chamber  110  of housing  12 . Also located in housing  12  is outlet  98  through which high pressure refrigerant can exit interior chamber  110 . 
   Thus, compressor  10  is a high side compressor in which interior chamber  110  is filled with discharge pressure refrigerant. The compressed refrigerant is at a higher temperature than the suction pressure refrigerant in passage  126 , and housing  12  can facilitate the cooling of the compressed refrigerant by absorbing heat therefrom. The present invention is not limited to high side compressors, however, and alternative embodiments may employ a variety of configurations including compressor designs wherein the interior chamber of the housing is at least partially filled with suction pressure refrigerant. 
   At the bottom of interior chamber  110  may be provided an oil sump  134  for containing a pool of a lubricant such as oil. In the embodiment shown in  FIG. 2 , a top surface  136  of the oil within interior chamber  110  is shown to be at approximately the same vertical level as spring washer  90 . Passages  124 ,  150  and  152  all open to the space located between stationary shaft  34  and roller  50  which is, therefore, at suction pressure. The pressure differential between the high pressure refrigerant within interior chamber  110  and the suction pressure refrigerant within longitudinal passage  126  and between stationary shaft  34  and roller  50  causes oil from sump  134  to flow upwardly through oil inlet  108  within reduced diameter portion  138  of longitudinal passage  126 . Portion  138  can extend approximately between radial passage  124  and oil inlet  108 . In fluid communication with narrow portion  138  are radially oriented oil supply passages or channels  150 ,  152  which can be at approximately the vertical level of bearing  86 . Passages  150 ,  152  allow oil from narrow portion  138  to reach and lubricate bearing  86 . 
   A portion of the lubricant oil may also flow far enough in an upward direction to exit longitudinal passage  126  through radial passage  124 . Further, a portion of the oil entrained in the suction pressure refrigerant will continue on through channel  114 , compression chamber  52  and discharge valve  118  before returning to interior chamber  110  where it migrates downwardly to the oil sump. Thus, the oil may lubricate rotor  28 , roller  50 , sides  154  of vane  54 , bushing  60 , slot  62 , and discharge valve  118 . 
   Assembly of compressor  10  may advantageously include first assembling compression assembly  30 . Initially, vane  54  is placed in slot  55  of rotor  28 , and vane  54  is secured to top end plate  70  by a pin  156  ( FIGS. 2 and 3 ) that is inserted through a throughhole  158  in vane  54  and into a recess  160  in plate  70 . Next, roller  50 , having guide bushing  60  press fit therein, is located in compression space  52  such that vane  54  engages slot  62  and rotor  28  is positioned in abutting contact with top end plate  70 . The exposed end of pin  156  at the opposite end of rotor  28  is then aligned with and inserted into a recess  162  in bottom end plate  74 . Bottom end plate  74  can then be secured to rotor  28  by bolts  22  inserted into throughholes in end plates  70 ,  74  and rotor  28 . 
   Thus, the outer radial end of vane  54  is fixed to rotor  28  and the inner radial end of vane  54  is also fixed by pin  156  which extends through vane  54  into both end plates  70 ,  74 . By fixing both ends of vane  54 , instead of having only the outer radial end of vane  54  fixed to rotor  28 , the stresses within vane  54  are significantly reduced thereby reducing the possibility of failure of the compressor due to the breakage of vane  54 . The reduction in stress in vane  54  and the fixing of both ends of vane  54  also help to minimize the deflection of vane  54  due to the forces applied to vane  54  by its driving of the rotation of roller  50 . Minimizing the deflection of vane  54  facilitates the non-binding sliding of bushing  60  relative to vane  54 . Although only one vane  54  is used in the illustrated embodiment, alternative embodiments of the present invention may employ multiple vanes to further subdivide the compression chamber into working pockets. 
   The following components can be successively press fit or otherwise placed on shaft  34 : metal washer  96 , bearing  84 , bearing  86 , compression assembly  30 , bearing  88 , metal washer  72 , and spring washer  90 . With distal tip  80  of shaft  34  extending through aperture  64 , the foregoing components can then be secured to shaft  34  by threadingly coupling holding nut  82  to distal tip  80 . Thus, compression assembly  30  is rotatably mounted on shaft  34 . Side wall  15  with stator  26  shrink fitted or otherwise attached thereto can be bonded to top wall  16  via a weld at location  18 . Base  14  can be bonded to side wall  15 , in turn, via a weld at location  17 . 
   Compression mechanism  30  is positioned within housing body portion  16  such that rotor  28  is aligned with stator  26 . By positioning compression chamber  52  within rotor  28  and circumscribing rotor  28 , compression chamber  52  and end plates  70  and  74  with stator  26 , the overall assembled axial extending length of compressor  10  is relatively limited and thereby provides a compact overall design that facilitates the flexible positioning of the compressor. The compact arrangement provided by the present invention can allow the axial length of the compressor to be reduced to approximately the same axial length as of the stator  26 . 
   During compressor operation, electrical current supplied to stator  26  via a terminal assembly (not shown) creates a magnetic flux which in turn causes rotation of rotor  28 . The rotation of rotor  28  drives the rotation of roller  50  about drive shaft  34  through vane  54  which is fixed relative to rotor  28  and is slidingly disposed relative to roller  50 . Referring to  FIGS. 3 and 4 , as rotor  28  and roller  50  rotate, vane  54  slides relative to slot  62  in bushing  60 , the semi-crescent-shaped suction pocket  56   a  defined within compression chamber  52  becomes progressively larger, and the semi-crescent-shaped compression pocket  56   b  defined within compression chamber  52  become progressively smaller, i.e., shrinks. As pocket  56   a  expands, refrigerant and oil is drawn into pocket  56   a  through channel  114 . As pocket  56   b  decreases in volume, the high-pressure mixture of refrigerant and oil is expelled through discharge passage  120  once the pressure within compression pocket  56   b  is sufficient to open discharge valve assembly  106 . 
   Channel  114  is in communication with suction pocket  56   a  and discharge passage  120  is in communication with compression pocket  56   b  throughout an entire 360 degree rotation of rotor  28  and roller  50  about shaft  34 . After refrigerant is drawn into a suction pocket  56   a , rotation of rotor  28  and roller  50  about shaft  34  causes suction pocket  56   a  to reach its maximum volume, as shown in  FIG. 3 . At this point, compression pocket  56   b  has been fully compressed to zero volume, and the refrigerant has been expelled through discharge passage  120 . Further rotation of rotor  28  and roller  50  from the point shown in  FIG. 3  begins the compression of the refrigerant, and transforms what was a suction pocket  56   a  into a compression pocket  56   b . The further rotation of rotor  28  and roller  50  also simultaneously begins expansion of a new suction pocket  56   a , as can be best seen by comparing  FIGS. 3 and 4 . The progressive reduction in size of the compression pocket and the compression of the refrigerant vapor disposed therein, with the compression pocket being in fluid communication with discharge valve assembly  106 , causes the pressure within the compression pocket to open the discharge valve assembly  106 . Compressed refrigerant is discharged from compression chamber  52  through discharge passage  120  and the discharge valve assembly  106  disposed within discharge valve cavity  112  formed in plate  70 , as best seen with reference to  FIG. 1 . 
   The discharge valve assembly includes a valve seat body  142  defining a discharge port  140  in fluid communication with compression chamber  52  via discharge passage  120 . The discharge valve assembly also includes a spherical valve member  144  biased into engagement with a valve seat defined by body  142  by spring  146  to thereby seal the discharge port. A retaining ring not shown) can be used to secure spring  146  within valve seat body  142 . When the fluid pressure within discharge pocket  56   b  exceeds the pressure necessary to overcome the biasing force of spring  146 , the valve will be forced open and refrigerant will be discharged from compression chamber  52  through discharge port  140 . The discharged refrigerant is then communicated through discharge cavity  112  to interior chamber  110 . The compressed refrigerant is discharged from compressor  10  through discharge fitting  128  to a system that utilizes compressed fluid such as a refrigeration system or heat pump system. 
   As described above, compression pocket  56   b  is in fluid communication with interior chamber  110  and oil sump  134  whenever the valve is open. Since the valve opens periodically, following the cyclical increase in pressure in a compression pocket  56   b , compression pocket  56   b  is periodically in fluid communication with interior chamber  110  and oil sump  134 . 
   In the embodiments described above, suction pocket  56   a  is continuously in fluid communication with longitudinal passage  126 . However, it may also be possible in other embodiments for suction pocket  56   a  to be periodically in fluid communication with longitudinal passage  126  via a one-way check valve. Such a check valve could be disposed within channel  114 , for example. 
   The compressor of the present invention has been described herein as rotating in a clockwise direction, i.e., in direction  102  shown in  FIG. 3 . However, it is to be understood that the motor can also be arranged such that the compressor rotates in a counterclockwise direction, i.e., opposite to direction  102 . With such a counterclockwise rotation, channel  114  may be disposed on a side of the vane opposite to that shown in  FIGS. 3 and 4 . That is, regardless of the direction of rotation, the vane may lead the channel in rotation. Further, regardless of the direction of rotation, discharge valve  118  may lead both the vane and the channel in rotation. Thus, regardless of the direction of rotation, the discharge valve may be in fluid communication with a compression pocket, and the channel may be in fluid communication with a suction pocket. 
   While this invention has been described as having an exemplary design, the present invention may be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles.