Abstract:
A discharge valve is provided for implementation between a discharge pressure zone and a discharge chamber. The discharge valve is operable between an open position for enabling fluid flow between the discharge pressure zone and the discharge chamber and a closed position for prohibiting fluid flow between the discharge pressure zone and the discharge chamber. The discharge valve includes a housing defining a cavity and having a flow aperture therethrough. A valve disc is slidably disposed within the housing and is operable for defining the open and closed positions of the discharge valve. The valve disc includes a contoured body for reducing stresses experienced within the valve disc and improving fluid flow therearound.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to compressors. More particularly the present invention relates to a discharge valve incorporating a contoured discharge valve disc.  
         BACKGROUND AND SUMMARY OF THE INVENTION  
         [0002]    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 which are caused to orbit relative to one another so as to define one or more moving chambers which progressively decrease in size as they travel from an outer suction port towards a center discharge port. An electric motor is normally provided to cause the relative orbiting scroll movement.  
           [0003]    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 the recompression volume. The recompression volume is the volume of the discharge chamber and 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.  
           [0004]    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 scroll members and any 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 obviously undesirable. The incorporation of a discharge valve can reduce or eliminate these reverse rotation problems.  
           [0005]    Traditional discharge valves include a flat disc that is operable between an open and a closed position for selectively enabling the flow of pressurized gas through the discharge valve. As a result of the pressure differential on either side of the flat disc the flat disc experiences significant, cyclical tensile stresses. Over time, these stresses may fatigue the flat disc and result in failures. To cope with these stresses, flat discs generally have a thicker profile and thus are heavier than desired. Increased weight results in slower response time as the disc moves between its open and closed positions.  
           [0006]    Therefore, it is desirable in the industry to provide a discharge valve assembly having an improved disc design. The improved disc design should reduce the tensile stresses the disc experiences due to pressure differentials and preferably improve the flow through the discharge valve for lowering the pressure differential, thereby lowering the experienced tensile stress. Further, in reducing the tensile stresses, the improved disc design should have a thinner profile, thereby reducing the weight of the disc and improving response of the disc to pressure changes.  
           [0007]    In a first embodiment, the present invention resides in the provision of a contoured disc valve in a scroll compressor, and in an alternative embodiment in a conventional single-vane rotary compressor.  
           [0008]    Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:  
         [0010]    [0010]FIG. 1 is a vertical sectional view through the center of a scroll compressor which incorporates a discharge valve assembly according to the principles of the present invention;  
         [0011]    [0011]FIG. 2 is an enlarged view of a floating seal assembly and the discharge valve assembly of the compressor of FIG. 1;  
         [0012]    [0012]FIG. 3 is an enlarged view of the discharge valve assembly in a closed position;  
         [0013]    [0013]FIG. 4 is an enlarged view of the discharge valve assembly in an open position;  
         [0014]    [0014]FIG. 5 is a vertical sectional view through the center of a conventional single-vane rotary compressor which incorporates the discharge valve assembly of the present invention; and  
         [0015]    [0015]FIG. 6 is a cross-sectional view in the direction of arrows  6 - 6  shown in FIG. 5.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]    The following description of the preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.  
         [0017]    At the outset, it is noted that the herein described compressor embodiments are the subject of commonly assigned U.S. Pat. No. 6,139,291 to Perevozchikov, the disclosure of which is incorporated herein be reference. 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  10  that incorporates a discharge valve assembly  12  in accordance with the present invention. Compressor  10  comprises a generally cylindrical hermetic shell  14  having welded at the upper end thereof a cap  16  and at the lower end thereof a base  18  having a plurality of mounting feet (not shown) integrally formed therewith. Cap  16  is provided with a refrigerant discharge fitting  20 . Other major elements affixed to shell  14  include a transversely extending partition  22  which is welded about its periphery at the same point that cap  16  is welded to shell  14 , a main bearing housing  24  which is suitably secured to shell  14  and a two piece upper bearing housing  26  suitably secured to main bearing housing  24 .  
         [0018]    A drive shaft or crankshaft  30  having an eccentric crank pin  32  at the upper end thereof is rotatably journaled in a bearing  34  in main bearing housing  24  and a second bearing  36  in upper bearing housing  26 . Crankshaft  30  has at the lower end a relatively large diameter concentric bore  38  which communicates with a radially outwardly inclined smaller diameter bore  40  extending upwardly therefrom to the top of crankshaft  30 . The lower portion of the shell interior defines an oil sump  42  which is filled with lubricating oil to a level slightly above the lower end of a rotor  46 , and bore  38  acts as a pump to pump lubricating oil up crankshaft  30  and into bore  40  and ultimately to all of the various portions of compressor  10  that require lubrication.  
         [0019]    Crankshaft  30  is rotatably driven by an electric motor  48  including a stator  50 , windings  52  passing therethrough and rotor  46  being press fit on crankshaft  30  and having upper and lower counterweights  54 ,  56 , respectively.  
         [0020]    An upper surface  58  of upper bearing housing  26  is provided with a flat thrust bearing surface on which is disposed an orbiting scroll member  60  having a spiral vane or wrap  62  extending upward from an end plate  64 . Projecting downwardly from a lower surface of end plate  64  of orbiting scroll member  60  is a cylindrical hub  66  having a journal bearing  68  therein and in which is rotatably disposed a drive bushing  70  having an inner bore  72  in which crank pin  32  is drivingly disposed. Crank pin  32  has a flat on one surface that engages a flat surface (not shown) formed in a portion of bore  72  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 herein by reference. An Oldham coupling  76  is also provided and positioned between orbiting scroll member  60  and upper bearing housing  26  and is keyed to orbiting scroll member  60  and a non-orbiting scroll member  80  to prevent rotational movement of orbiting scroll member  60 . Oldham coupling  76  is preferably 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.  
         [0021]    Non-orbiting scroll member  80  is also provided having a wrap  82  extending downwardly from an end plate  84  that is positioned in meshing engagement with wrap  62  of orbiting scroll member  60 . Non-orbiting scroll member  80  has a centrally disposed discharge passage  86  that communicates with an upwardly open recess  88  that in turn is in fluid communication with a discharge muffler chamber  90  defined by cap  16  and the partition  22 . An annular recess  92  is also formed in non-orbiting scroll member  80 , within which is disposed a floating seal assembly  94 . Recesses  88 ,  92  and floating seal assembly  94  cooperate to define an axial pressure biasing chamber which receives pressurized fluid being compressed by wraps  62 ,  82  so as to exert an axial biasing force on the non-orbiting scroll member  80  to thereby urge tips of the respective wraps  62 ,  82  into sealing engagement with opposed end plate surfaces  98 ,  100  of end plates  64 ,  84 , respectively. Floating seal assembly  94  is preferably of the type described in greater detail in U.S. Pat. No. 5,156,539, the disclosure of which is incorporated herein by reference. Non-orbiting scroll member  80  is designed to be mounted to main bearing housing  24  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 incorporated herein by reference.  
         [0022]    Referring now to FIG. 2 floating seal assembly  94  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 portion  106 . Above gasket assembly  108  is disposed an annular spacer plate  110  having a plurality of equally spaces holes that also mate with and receive base portion  106 . Above spacer plate  110  is an annular gasket assembly  112  having a plurality of equally spaced holes that mate with and receive projections  104 . Seal assembly  94  is held together by an annular upper seal plate  114  that has a plurality of equally spaced holes mating with and receiving projections  104 . Seal plate  114  includes a plurality of annular projections  116  that mate with and extend into the plurality of holes in annular gasket assembly  112  and spacer plate  110  to provide stability to seal assembly  94 . Seal plate  114  also includes an annular upwardly projecting planar sealing lip  118 . Seal assembly  94  is secured together by swaging the ends of projections  104  as indicated at  120 .  
         [0023]    Seal assembly  94  therefore provides three distinct seals. First, an inside diameter seal at two interfaces  122 , second, an outside diameter seal at two interfaces  124  and a top seal  126 . Seals  122  isolate fluid under intermediate pressure in the bottom of annular recess  92  from fluid in recess  88 . Seals  124  isolate fluid under intermediate pressure in the bottom of annular recess  92  from fluid within shell  14 . Seal  126  is between sealing lip  118  and an annular seat portion on partition  22 . The seal  126  isolates fluid at suction pressure from fluid at discharge pressure across the top of seal assembly  94 .  
         [0024]    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  94  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 de-energizing motor. The width of seal  126  is chosen so that the unit pressure between the sealing lip  118  and the seat portion of partition  22  is greater than normally encountered discharge pressure, thus ensuring consistent sealing.  
         [0025]    Scroll compressor  10  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.  
         [0026]    The present invention is directed towards normally closed mechanical discharge valve assembly  12  that is disposed within recess  88  that is formed in non-orbiting scroll member  80 . Discharge valve assembly  12  moves between a fully closed and a fully open condition during steady state operation of compressor  10 . Valve assembly  12  will close during the shut down of compressor  10 . When valve assembly  12  is fully closed, the recompression volume is minimized and the reverse flow of discharge gas through scroll members  60 ,  80  is prohibited. Valve assembly  12  is normally closed as shown in FIGS. 2 and 3. The normally closed configuration for valve assembly  12  requires a discharge force (i.e. pressure differential) to open valve assembly  12 . Valve assembly  12  relies on mechanical biasing for closing.  
         [0027]    Referring now to FIGS. 2 through 4, discharge valve assembly  12  includes a housing  130 , a spring  132 , a contoured disc  134  and a valve plate  136 . Spring  132  seats within a cavity  138  of housing  130  against an inner face  140  of a top wall  142  of housing  130 . A series of flow orifices  144  are disposed through the top wall  142  of housing  130 . Contoured disc  134  is operably interconnected with spring  132 , whereby spring  132  biases contoured disc  134  downward within cavity  138 . Valve plate  136  seats within a recess  146  of housing  130  and includes a flow aperture  148  therethrough. Flow aperture  148  is in direct fluid communication with discharge passage  86  of non-orbiting scroll member  80 . Spring  132  biases contoured disc  134  into sealed contact with valve plate  136 , thereby defining the closed configuration. The present embodiment of contoured disc  134  is provided as a dome-shaped disc. The domed disc provides an advantage of more stable flow through discharge valve assembly  12 , thereby reducing the pressure difference thereacross. Further advantages are seen in the reduction of tensile stress that the contoured disc experiences, as discussed in further detail below.  
         [0028]    Discharge valve assembly  12  is assembled into non-orbiting scroll member  80  by housing  130  seating within recess  88  with flow orifices  144  facing upward. Valve plate  136  seats within recess  146  against a bottom face  150  of recess  146 . A retainer  152  is installed within recess  88  to maintain the assembly of discharge valve assembly  12  in non-orbiting scroll member  80 . Retainer  152  can be connected to non-orbiting scroll member  80  by being press fit within recess  88 . Alternatively, retainer  152  and recess  88  can be threaded to provide the connection or other means known in the art can be used to secure retainer  152  within recess  88 . The assembly of retainer  152  sandwiches the entire discharge valve assembly  12  between the bottom surface of recess  88  and retainer  152 .  
         [0029]    Discharge valve assembly  12  is normally biased in its closed position with contoured disc  134  abutting an upper flat surface of valve plate  136 , thereby providing the closed configuration. This prohibits fluid flow from discharge muffler chamber  90  into the compression pockets formed by scroll members  60 ,  80 . In order to open discharge valve assembly  12 , fluid pressure within discharge passage  86  biases contoured disc  134  against the biasing force of spring  132 . This occurs when the fluid pressure in discharge passage  86  is greater than the fluid pressure within muffler chamber  90 . During operation of compressor  10 , the fluid pressure differential between fluid in muffler chamber  90  and fluid within discharge passage  86  will move contoured disc  134  between abutment with surface of valve plate  136  and an intermediate position within cavity  138  (i.e. between a closed position and an open position). As best seen in FIG. 4, when contoured disc  134  is in an intermediate position within cavity  138 , fluid flow (represented with arrows) is enabled from discharge passage  86 , through flow aperture  148  of valve plate  136 , around the periphery of contoured disc  134  and out to muffler chamber  90  through flow orifices  144 . Discharge valve assembly  12  of the present invention operates solely on pressure differentials. The unique design of contoured disc  134  provides a stronger component to improve the durability of the system.  
         [0030]    More specifically, tensile stress is present in contoured disc  134  as a result of the pressure difference thereacross. Given a traditional flat disc, flooded start failures of compressors may occur due to failure of the disc under cyclical tensile loads. The present invention, by providing a contoured disc, significantly reduces the stress loading experienced by the disc. In fact, use of a contoured disc can reduce stress loading by a factor of four (4), without increasing the disc thickness. As discussed above, the present embodiment provides a domed disc. It will be appreciated, however that contoured disc  134  may include any one of a variety of contoured forms. The domed-disc of the present embodiment includes an apex that is directed toward discharge passage  86 . In this manner, smooth fluid flow around contoured disc  134  is enabled. The smooth fluid flow reduces the pressure differential experienced across contoured disc  134 , thereby further reducing stress loading therein.  
         [0031]    Referring now to FIGS. 5 and 6, a rotary compressor  200  is illustrated which incorporates a discharge valve assembly  12 ′ in accordance with the present invention. Compressor  200  comprises a housing  202 , a shaft  204  that is connected to a motor  206  provided in housing  202 , a roller  208  eccentrically mounted at the lower end of shaft  204 , and a cylinder  210  enclosing roller  208  as shown in FIG. 5. An eccentric  212  (FIG. 6) is attached to shaft  204  and is freely movably disposed in roller  208 . A valve  214  is provided and disposed on a wall of cylinder  210 . A spring  216  continuously urges valve  214  against roller  208 . As shaft  204  is rotated by motor  206 , roller  208  rotates in an eccentric manner to compress refrigerant taken into a suction area  218  through a suction pipe  220 . Pressurized gas is discharged from a discharge area  222  of cylinder  210  and discharges through a pipe  224  provided at the top of housing  202 . Cylinder  210  defines a recess  226  within which is located discharge valve assembly  12 ′. Cylinder  210  further defines a discharge passage  240  in fluid communication with recess  226  and discharge valve assembly  12 ′.  
         [0032]    Discharge valve assembly  12 ′ is disposed within recess  226  and includes a housing  130 ′, a spring  132 ′, a contoured disc  134 ′ and a valve plate  136 ′. Spring  132 ′ seats within a cavity  138 ′ of housing  130 ′ against an inner face  140 ′ of a top wall  142 ′ of housing  130 ′. A series of flow orifices  144 ′ are disposed through top wall  142 ′ of housing  130 ′. Contoured disc  134 ′ is operably interconnected with spring  132 ′, whereby spring  132 ′ biases contoured disc  134 ′ downward within cavity  138 ′. Valve plate  136 ′ seats within a recess  146 ′ of housing  130 ′ and includes a flow aperture  148 ′ therethrough. Flow aperture  148 ′ is in direct fluid communication with discharge passage  240  of cylinder  210 . Spring  132 ′ biases contoured disc  134 ′ into sealed contact with valve plate  136 ′, thereby defining the closed configuration. Discharge valve assembly  12 ′ is held into recess  226  by a press-fit retainer  238 .  
         [0033]    The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.