Abstract:
A scroll machine includes a shell defining a discharge chamber, a first scroll member having a first spiral wrap projecting outwardly from a first end cap, a second scroll member having a second spiral wrap projecting outwardly from a second end cap intermeshed with the first spiral wrap, and a drive member causing the scroll members to orbit relative to one another. The spiral wraps create pockets of progressively changing volume between a suction pressure zone and a discharge pressure zone with the discharge pressure zone being in communication with the discharge chamber. A discharge valve assembly is disposed between the discharge pressure zone and the discharge chamber and is movable relative to the first scroll member. The discharge valve assembly includes a valve plate movable between a first open state and a closed state.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a continuation of U.S. patent application Ser. No. 10/671,049 filed on Sep. 25, 2003. The disclosure of the above application is incorporated herein by reference. 
     
    
     FIELD  
       [0002]     The present disclosure relates to rotary compressors. More particularly the present disclosure relates to a direct discharge valve system that is utilized in a compressor.  
       BACKGROUND AND SUMMARY  
       [0003]     Scroll machines are becoming more and more popular for use as compressors in both refrigeration as well as air conditioning and heat pump applications due primarily to their capability for extremely efficient operation. Generally, these machines incorporate a pair of intermeshed spiral wraps, one of which is caused to orbit relative to the other so as to define one or more moving chambers that progressively decrease in size as they travel from an outer suction port towards a center discharge port. An electric motor is normally provided that operates to drive the orbiting scroll member via a suitable drive shaft.  
         [0004]     Because scroll compressors depend upon successive chambers for suction, compression, and discharge processes, suction and discharge valves in general are not required. However, the performance of the compressor can be increased with the incorporation of a discharge valve. One of the factors that will determine the level of increased performance is the reduction of what is called recompression volume. The recompression volume is the volume of the discharge chamber and the discharge port of the compressor when the discharge chamber is at its smallest volume. The minimization of this recompression volume will result in a maximizing of the performance of the compressor. In addition, when such compressors are shut down, either intentionally as a result of the demand being satisfied, or unintentionally as a result of a power interruption, there is a strong tendency for the backflow of compressed gas from the discharge chamber and to a lesser degree for the gas in the pressurized chambers to effect a reverse orbital movement of the orbiting scroll member and its associated drive shaft. This reverse movement often generates noise or rumble, which may be considered objectionable and undesirable. Further, in machines employing a single phase drive motor, it is possible for the compressor to begin running in the reverse direction should a momentary power interruption be experienced. This reverse operation may result in overheating of the compressor and/or other inconveniences to the utilization of the system. Additionally, in some situations, such as a blocked condenser fan, it is possible for the discharge pressure to increase sufficiently to stall the drive motor and effect a reverse rotation thereof. As the orbiting scroll orbits in the reverse direction, the discharge pressure will decrease to a point where the motor again is able to overcome this pressure head and orbit the scroll member in the forward direction. However, the discharge pressure will again increase to a point where the drive motor is stalled and the cycle is repeated. Such cycling is undesirable in that it is self-perpetuating. The incorporation of a discharge valve can reduce or eliminate these reverse rotation problems.  
         [0005]     scroll machine includes a shell defining a discharge chamber, a first scroll member having a first spiral wrap projecting outwardly from a first end cap, a second scroll member having a second spiral wrap projecting outwardly from a second end cap intermeshed with the first spiral wrap, and a drive member causing the scroll members to orbit relative to one another. The spiral wraps create pockets of progressively changing volume between a suction pressure zone and a discharge pressure zone with the discharge pressure zone being in communication with the discharge chamber. A discharge valve assembly is disposed between the discharge pressure zone and the discharge chamber and is movable relative to the first scroll member. The discharge valve assembly includes a valve plate movable between a first open state and a closed state.  
         [0006]     Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]     The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.  
         [0008]      FIG. 1  is a vertical sectional view through the center of a scroll compressor that incorporates a retention system for a discharge valve assembly in accordance with the present disclosure;  
         [0009]      FIG. 2  is a top elevational view of the compressor shown in  FIG. 1  with the cap and a portion of the partition removed;  
         [0010]      FIG. 3  is an enlarged view of the floating seal assembly and discharge valve assembly illustrated in  FIG. 1 ;  
         [0011]      FIG. 4A  is an enlarged view of the discharge valve assembly illustrated in  FIGS. 1 and 3  with the discharge valve being biased against the non-orbiting scroll member;  
         [0012]      FIG. 4B  is an enlarged view of the discharge valve assembly illustrated in  FIGS. 1 and 3  with the discharge valve being spaced from the non-orbiting scroll member; and  
         [0013]      FIG. 5  is an exploded perspective view of the retention system of the discharge valve assembly shown in  FIGS. 1 and 3 . 
     
    
     DETAILED DESCRIPTION  
       [0014]     The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.  
         [0015]     Referring now to the drawings in which like reference numerals designate like or corresponding parts throughout the several views, there is shown. in  FIG. 1 a  scroll compressor that incorporates a retention system for a discharge valving system in accordance with the present disclosure and which is designated generally by reference numeral  10 . Compressor  10  comprises a generally cylindrical hermetic shell  12  having welded at the upper end thereof a cap  14  and at the lower end thereof a base  16  having a plurality of mounting feet (not shown) integrally formed therewith. Cap  14  is provided with a refrigerant discharge fitting  18 . Other major elements affixed to the shell include a transversely extending partition  22  that is welded about its periphery at the same point that cap  14  is welded to shell  12 , a lower bearing housing  24  that is suitably secured to shell  12  and a two piece upper bearing housing  26  suitably secured to lower bearing housing  24 .  
         [0016]     A drive shaft or crankshaft  28  having an eccentric crank pin  30  at the upper end thereof is rotatably journaled in a bearing  32  in lower bearing housing  24  and a second bearing  34  in upper bearing housing  26 . Crankshaft  28  has at the lower end a relatively large diameter concentric bore  36  that communicates with a radially outwardly inclined smaller diameter bore  38  extending upwardly therefrom to the top of crankshaft  28 . The lower portion of the interior shell  12  defines an oil sump  40  that is filled with lubricating oil to a level slightly above the lower end of a rotor  42 , and bore  36  acts as a pump to pump lubricating fluid up crankshaft  28  and into bore  38  and ultimately to all of the various portions of the compressor that require lubrication.  
         [0017]     Crankshaft  28  is rotatively driven by an electric motor including a stator  46 , windings  48  passing therethrough and rotor  42  press fitted on crankshaft  28  and having upper and lower counterweights  50  and  52 , respectively.  
         [0018]     The upper surface of upper bearing housing  26  is provided with a flat thrust bearing surface  54  on which is disposed an orbiting scroll member  56  having the usual spiral vane or wrap  58  extending upward from an end plate  60 . Projecting downwardly from the lower surface of end plate  60  of orbiting scroll member  56  is a cylindrical hub having a journal bearing  62  therein and in which is rotatively disposed a drive bushing  64  having an inner bore  66  in which crank pin  30  is drivingly disposed. Crank pin  30  has a flat on one surface that drivingly engages a flat surface (not shown) formed in a portion of bore  66  to provide a radially compliant driving arrangement, such as shown in Assignee&#39;s U.S. Pat. No. 4,877,382, the disclosure of which is hereby incorporated reference. An Oldham coupling  68  is also provided positioned between orbiting scroll member  56  and bearing housing  24  and keyed to orbiting scroll member  56  and a non-orbiting scroll member  70  to prevent rotational movement of orbiting scroll member  56 . Oldham coupling  68  may be of the type disclosed in Assignee&#39;s co-pending U.S. Pat. No. 5,320,506, the disclosure of which is hereby incorporated herein by reference.  
         [0019]     Non-orbiting scroll member  70  is also provided having a wrap  72  extending downwardly from an end plate  74  that is positioned in meshing engagement with wrap  58  of orbiting scroll member  56 . Non-orbiting scroll member  70  has a centrally disposed discharge passage  76  that communicates with an upwardly open recess  78  which, in turn, is in fluid communication with a discharge muffler chamber  80  defined by cap  14  and partition  22 . An annular recess  82  is also formed in non-orbiting scroll member  70  within which is disposed a floating seal assembly  84 . Recesses  78  and  82  and seal assembly  84  cooperate to define axial pressure biasing chambers, which receive pressurized fluid being compressed by wraps  58  and  72  so as to exert an axial biasing force on non-orbiting scroll member  70  to thereby urge the tips of respective wraps  58 ,  72  into sealing engagement with the opposed end plate surfaces of end plates  74  and  60 , respectively. Seal assembly  84  may be of the type described in greater detail in U.S. Pat. No. 5,156,539, the disclosure of which is hereby incorporated herein by reference. Non-orbiting scroll member  70  is designed to be mounted to upper bearing housing  26  in a suitable manner such as disclosed in the aforementioned U.S. Pat. No. 4,877,382 or U.S. Pat. No. 5,102,316, the disclosures of which are hereby incorporated herein by reference.  
         [0020]     Referring now to  FIGS. 2 and 3 , floating seal assembly  84  is of a coaxial sandwiched construction and comprises an annular base plate  102  having a plurality of equally spaced upstanding integral projections  104  each having an enlarged base portion  106 . Disposed on plate  102  is an annular gasket assembly  108  having a plurality of equally spaced holes that mate with and receive base portions  106 . On top of gasket assembly  108  is disposed an annular spacer plate  110  having a plurality of equally spaces holes that also mate with and receive base portions  106 . On top of plate  110  is an annular gasket assembly  112  having a plurality of equally spaced holes that mate with and receive projections  104 . The assembly of seal assembly  84  is maintained by an annular upper seal plate  114 , which has a plurality of equally spaced holes mating with and receiving projections  104 . Seal plate  114  includes a plurality of annular projections  116 , which mate with and extend into the plurality of holes in annular gasket assembly  112  and spacer plate  110  to provide stability to seal assembly  84 . Seal plate  114  also includes an annular upwardly projecting planar sealing lip  118 . Seal assembly  84  is secured together by swaging the ends of projections  104  as indicated at  120 .  
         [0021]     Referring now to  FIG. 3 , seal assembly  84  therefore provides three distinct seals: first, an inside diameter seal at two interfaces  122 ; second, an outside diameter seal at two interfaces  124 ; and, third, a top seal at  126 . Seals  122  isolate fluid under intermediate pressure in the bottom of recess  82  from fluid under discharge pressure in recess  78 . Seals  124  isolate fluid under intermediate pressure in the bottom of recess  82  from fluid under suction pressure within shell  12 . Seal  126  is between sealing lip  118  and an annular seat portion on partition  22 . Seal  126  isolates fluid at suction pressure from fluid at discharge pressure across the top of seal assembly  84 .  
         [0022]     The diameter and width of seal  126  are chosen so that the unit pressure between sealing lip  118  and the seat portion on partition  22  is greater than normally encountered discharge pressure, thus ensuring consistent sealing under normal operating conditions of compressor  10 , i.e., at normal operating pressure ratios. Therefore, when undesirable pressure conditions are encountered, seal assembly  84  will be forced downward breaking seal  126 , thereby permitting fluid flow from the discharge pressure zone of compressor  10  to the suction pressure zone of compressor  10 . If this flow is great enough, the resultant loss of flow of motor-cooling suction gas (aggravated by the excessive temperature of the leaking discharge gas) will cause a motor protector to trip thereby the de-energizing motor. The width of seal  126  is chose so that the unit pressure between sealing lip  118  and the seat portion of partition  22  is greater than normally encountered discharge pressure, thus ensuring consistent sealing.  
         [0023]     The scroll compressor as thus far broadly described is either now known in the art or is the subject of other pending applications for patent or patents of Applicant&#39;s Assignee.  
         [0024]     The present disclosure is directed towards a retention system for a normally open mechanical valve assembly  130 , which is disposed within recess  78 , which is formed in non-orbiting scroll member  70 . While the present disclosure is being described in conjunction with normally open mechanical valve assembly  130 , the retention system of the present disclosure can be used with any other type of discharge valve also. Valve assembly  130  moves between a first or closed condition, a second or open condition, and a third or fully open condition during steady state operation of compressor  10 . Valve assembly  130  will close during the shut down of compressor  10 . When valve assembly  130  is fully closed, the recompression volume is minimized and the reverse flow of discharge gas through scroll members  56  and  70  is prohibited. Valve assembly  130  is normally open as shown in  FIGS. 3 and 4 A. The normally open configuration for valve assembly  130  eliminates the force required to open valve assembly  130  as well as eliminating any mechanical device needed to close valve assembly  130 . Valve assembly  130  relies on gas pressure differential for closing.  
         [0025]     Referring now to  FIGS. 3-5 , discharge valve assembly  130  is disposed within recess  78  and it comprises a valve seat  132 , a valve plate  134 , a valve stop  136  and a wave ring retainer  138 . Valve seat  132  is a flat metal disc shaped member defining a discharge passage  140 , a pair of alignment apertures  142  and a cavity  144 . Non-orbiting scroll member  70  defines a pair of alignment bores. When apertures  142  are in registry with the alignment bores, discharge passage  140  is aligned with discharge passage  76 . The shape of discharge passage  140  is the same as discharge passage  76 . The thickness of valve seat  132 , particularly in the area of cavity  144  is minimized to minimize the recompression volume for compressor  10 , which increases the performance of compressor  10 . The bottom surface of cavity  144  adjacent to valve plate  134  includes a contoured surface  148 . The flat horizontal upper surface of valve seat  132  is used to secure valve plate  134  around its entire circumference. Contoured surface  148  of cavity  144  provides for the normally open characteristic of valve assembly  130 . Contoured surface  148  may be a generally planar surface a shown in  FIG. 4A  or contoured surface  148  may be a curved surface. While cavity  144  and contoured surface  148  are shown as a pocket within valve seat  132 , it is within the scope of the present disclosure to have cavity  144  and thus surface  148  extend through the edge of valve seat  132 . Also, it is within the scope of the present disclosure to eliminate valve seat  132  and incorporate cavity  144  and surface  148  directly into and onto non-orbiting scroll  70  if desired.  
         [0026]     Valve plate  134  is a flat thin metal disc shaped member that includes an annular ring  150 , a generally rectangular portion  152  extending radially inward from ring  150  and a generally circular portion  154  attached to the radial inner end of rectangular portion  152 . Rectangular portion  152  is designed to be smaller in width than circular portion  154 . This reduced section therefore has a lower bending load than circular portion  154 , which results in a faster opening of valve assembly  130 . This reduced section of rectangular portion  152  is acceptable from a durability standpoint since contoured surface  148  reduces the stress loading on this reduced section. The size and shape of portion  154  is designed to completely cover discharge passage  140  of valve seat  132 . The generally circular shape of portion  154  eliminates valve breakage that is associated with rectangular valve plates. In general, valve plates can have a tendency to twist during the closing of the valve due to the pressure fluctuations across the valve. When a rectangular shape valve twists before closing, the outside corner of the rectangle will hit first causing high loading and the breakage of the corner. The present disclosure, by using a generally circular portion to close the valve, eliminates the possibility of this corner breakage. Valve plate  134  also includes a pair of bosses  156 , which define a pair of alignment apertures  158 . When apertures  158  are in registry with apertures  142  of valve seat  132 , rectangular portion  152  positions circular portion  154  in alignment with discharge passage  140 . The thickness of valve plate  134  is determined by the stresses developed in rectangular portion  152  as valve plate  134  deflects from its closed position to its open position as described below.  
         [0027]     Valve stop  136  is a thick metal disc shaped member that provides support and backing for valve plate  134  and valve seat  132 . Valve stop  136  is similar in configuration to valve plate  134  and includes an annular ring  160 , a generally rectangular portion  162  extending radially inward from ring  160 , a generally circular portion  164  attached to the radially inner end of rectangular portion  162  and a support section  166  extending between circular portion  164  and ring  160  on the side of portion  164  opposite to portion  162 . Valve stop  136  also includes a pair of bosses  168 , which define a pair of alignment apertures  170 . When apertures  170  are in registry with apertures  158  in valve plate  134 , rectangular portion  162  is aligned with rectangular portion  152  of valve plate  134  and it positions circular portion  164  in alignment with circular portion  154  of valve plate  134 . Rectangular portion  162  and circular portion  164  cooperate to define a curved contoured surface  172 .  
         [0028]     Discharge valve assembly  130  is assembled to non-orbiting scroll member  70  by first placing valve seat  132  within recess  78  with contoured surface  148  facing upward while aligning apertures  142  with bores  146 , which aligns passage  140  with passage  76 . Next, valve plate  134  is placed on top of valve seat  132  within recess  78  while aligning apertures  158  with apertures  142 , which aligns circular portion  154  with passage  140 . Next, valve stop  136  is placed on top of valve plate  134  within recess  78  while aligning apertures  170  within apertures  158 , which aligns portions  162  and  164  with portions  152  and  154 , respectively. A roll pin  176  is inserted through each aligned set of apertures  170 ,  158  and  142  and press fit into each bore  146  to maintain the alignment of these components. Finally, retainer  138  is installed within recess  78  to maintain the assembly of valve assembly  130  with non-orbiting scroll member  70 . The assembly of retainer  138  sandwiches the entire annular ring  150  of valve seat  132  between the upper flat surface of valve seat  132  and ring  160  of valve stop  136  to secure and retain valve plate  134 .  
         [0029]     Retainer  138  is a wave ring retainer that is disposed within a groove  180  formed into recess  78  of non-orbiting scroll member  70 . The wave shape of retainer  138  causes it to engage both the upper surface  182  and the lower surface  184  of groove  180  to adequately retain discharge valve assembly within recess  78 , as shown in  FIG. 4A . The wave shape of retainer  138  also allows for axial movement of discharge valve assembly due to the resilience and, thus, compression of the wave ring retainer as shown in  FIG. 4B .  
         [0030]     Discharge valve assembly  130  is normally in a condition wherein valve plate  134  abuts the upper flat surface on valve seat  132 . Contoured surface  148  spaces valve plate  134  from valve seat  132  to provide for the normally open characteristic of valve assembly  130 . This allows limited fluid flow from discharge muffler chamber  80  into the compression pockets formed by scroll members  56  and  70 . In order to close valve assembly  130 , fluid pressure within muffler chamber  80  biases valve plate  134  against contoured surface  148  of valve seat  132  when the fluid pressure in chamber  80  is greater than the fluid pressure within the central most fluid pocket formed by scroll members  56  and  70 . During operation of compressor  10 , the fluid pressure differential between fluid in discharge chamber  80  and fluid within the central most fluid pocket formed by scroll members  56  and  70  will move valve plate  134  between abutment with contoured surface  148  of valve seat  132  and abutment with valve stop  136  or between a first closed position and a second open position. The normally open position of valve assembly  130  eliminates the force that is required to open a typical discharge valve. The elimination of this force lowers the pressure differential for operating the valve, which, in turn, lowers power losses. In addition the normally open feature reduces the sound generated during the closing of the valve due to the gradual closing of the valve rather than the sudden closure of a normally closed valve. Contoured surface  148  provides for this gradual closing feature. The valve of the present disclosure operates solely on pressure differentials. Finally, the unique design for valve assembly  130  provides a large flow area to improve the flow characteristics of the system.  
         [0031]     When valve plate  134  is in its second or open position, additional discharge pressure within discharge passage will react against discharge valve assembly  130  and it will eventually exceed the spring force being applied by wave ring retainer  138 . Discharge valve assembly  130  will then move axially upward to the position shown in  FIG. 4B , the third or fully open position, to allow fluid flow around the outer periphery of discharge valve assembly  130 .  
         [0032]     Valve plate  134  is sandwiched between valve seat  132  and valve stop  136  with annular ring  160  of valve stop  136  abutting annular ring  150  of valve plate  134 , which, in turn, abuts the upper flat surface of valve seat  132 . Rectangular portion  152  and circular portion  154  normally lie in an unstressed condition in a generally horizontal position as shown in  FIG. 4A . The deflection of valve plate  134  occurs in rectangular portion  152  and circular portion  154 . To fully close, portions  152  and  154  deflect toward valve seat  132  and to open portions  152  and  154  deflect in the opposite direction toward valve stop  136 . The stresses encountered by valve plate  134  are stresses that are both plus and minus in direction from the neutral normally open position. Thus, when comparing the stresses of valve plate  134  with those encountered by the flap valve of a normally closed discharge valve, the stresses are significantly reduced. The normally closed flap valve begins in a position adjacent a valve seat when the flap valve is unstressed. As the valve begins to open the stresses begin at the unstressed condition and continue to grow as the flap valve opens. Thus they are unidirectional from the unstressed condition. The present disclosure, by centering the stressed conditions of valve plate  134  on both sides of the unstressed condition, significantly reduces the stress loading experienced by valve plate  134 .  
         [0033]     In order to further reduce the stress loading and thus the life of valve plate  134 , the shape of contoured surface  148  of valve seat  132  and contoured surface  172  of valve stop  136  are chosen to ensure a gradual loading and minimizing of the stresses by distributing the loads over a broader area. Finally, the rounded contours and transitions between ring  150 , rectangular portion  152  and circular portion  154  are designed to eliminate stress risers. This elimination of stress risers, the equal distribution of the load and the reduction in the maximum stresses encountered significantly improves the life and performance for discharge valve assembly  130 .