Abstract:
A face of a base of an orbiting scroll member is aligned with a thrust bearing. The thrust bearing includes a back pressure pocket and a seal for sealing the back pressure pocket to entrap a compressed fluid. There is a tap for tapping fluid at a discharge pressure into said back pressure pocket.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This application relates to a scroll compressor wherein a back pressure pocket is provided with a fluid supply from a discharge pressure chamber. 
         [0002]    Scroll compressors are becoming widely utilized in fluid compression applications. In a scroll compressor, a pair of scroll elements each have a base and a generally spiral wrap extending from their base. The wraps interfit to define compression chambers. One of the two scroll elements is caused to orbit relative to the other, and as this orbiting occurs, compression chambers define between the wraps decrease in volume and an entrapped fluid is compressed. 
         [0003]    There are many challenges with a scroll compressor. One challenge is that the internal pressure in the compression chambers tends to force the two scroll members away from each other. To address this challenge, a bias force is applied to urge the two scroll members together. 
         [0004]    Scroll compressors are formed with a thrust bearing that acts in opposition to the bias force. The bias force is known to be behind a non-orbiting scroll member in some scroll compressors, and behind the orbiting scroll member in other scroll compressors. In scroll compressors wherein the bias force is placed behind the non-orbiting scroll member, the thrust bearing is on a rear face of the base of the orbiting scroll member. In scroll compressors wherein the bias force is behind the rear face of the orbiting scroll member, the thrust bearing is positioned at radially outer locations on a forward face. 
         [0005]    It is known to use a seal that receives a partially compressed fluid as part of the thrust bearing. Typically, a tap taps fluid at an intermediate compression point to a seal chamber. 
         [0006]    There are deficiencies with this arrangement. In particular, there are losses due to the cyclic feeding and draining of this back pressure pocket across the tap hole, as the tap hole orbits relative to the pocket. The fluid can actually be bypassed from one compression pocket to the next, with resulting efficiency losses. In addition, the width of the seal chamber must be sufficiently wide so the tap will always be in communication throughout the orbiting cycle. 
       SUMMARY OF THE INVENTION 
       [0007]    A face of a base of an orbiting scroll member is in contact with a thrust bearing. The thrust bearing includes a back pressure pocket and a seal for sealing the back pressure pocket to entrap a compressed fluid. There is a tap for tapping fluid at the discharge pressure into said back pressure pocket. 
         [0008]    These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a cross-sectional view through a scroll compressor incorporating the present invention. 
           [0010]      FIG. 2  is an enlarged view of a portion of the  FIG. 1  compressor. 
           [0011]      FIG. 3  shows a detail of a seal element. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0012]      FIG. 1  shows a compressor  20  incorporating a shaft  22  that is driven to rotate by a motor (not shown).  FIG. 2  shows a portion of the compressor  20 . The shaft causes an orbiting scroll member  24  to orbit through a non-rotation coupling, as known. The orbiting scroll member  24  has a wrap which interfits with a wrap on a non-orbiting scroll member  26 . As shown, a force F biases one of the scroll elements toward the other. In the  FIG. 1  embodiment, the bias force F is directed to urge the non-orbiting scroll member  26  toward the orbiting scroll member  24 . The bias force may be created by a tapped compressed fluid, or by a mechanical element such as a spring. The bias element is disclosed here schematically by the letter F, and a worker of ordinary skill in the art would recognize how to provide such a bias force. 
         [0013]    As the two scroll members  24  and  26  orbit relative to each other, fluid is compressed in compression chambers defined between the wraps of the two scroll members  24  and  26 . This fluid is compressed toward a central discharge port  27 , and discharged into a discharge pressure chamber  28 . 
         [0014]    While this application will refer to the scroll wraps as being “generally spiral,” it should be understood that this term would extend to so-called “hybrid” wrap scroll compressors wherein the shape of a scroll wrap is a series of connected curves, rather than a pure spiral. Still, all scroll wraps do extend along curves from a central point radially outwardly, and wrapping around each other. The term “generally spiral” as used in this application extends to all such shapes. While the force is shown behind the non-orbiting scroll member  26 , it is also known to apply a bias force behind the orbiting scroll member  24 , and the teachings of this invention would extend to such a scroll compressor. 
         [0015]    As shown, a tap  30  taps this discharge pressure fluid downwardly, and radially inward through a crankcase passage  32 , into a passage  33  through a thrust bearing  34 . As shown, passage  30  is radially outwardly of the scroll members  24  and  26 . This fluid passes into the back pressure pocket  36 . 
         [0016]    As shown in  FIGS. 2 and 3 , a ring  38  has o-rings at radially outer and radially inner locations to seal the pocket  36 . Of course, other seal types may be used. A passage  48  is provided through the ring  38  to connect its lower and its upper face. The upper face of the ring is provided with a groove defining two lips  50  and  52  able to seal the pocket when the ring is in contact with the wear plate  44 . Pressure distribution on both sides of the ring maintain it in contact with the wear plate, and allow fluid at discharge pressure to act at the rear of the orbiting scroll. In this manner, a force is provided to resist a thrust of an orbiting scroll member  24  downwardly, and away from the non-orbiting scroll  26 . 
         [0017]    The thrust bearing  34  may be a sintered impregnated bronze thrust bearing. 
         [0018]    With the invention, the radial width of the back pressure chamber  36  may be made smaller than in the prior art. The back pressure chamber  36  will always communicate with its pressure source, and the orbit radius will not matter. Also, the discharge pressure will be at a more constant pressure than the intermediate pressure as used in the prior art. 
         [0019]    While the thrust bearing  34  is shown on a rear face of the base of an orbiting scroll member  24 , scroll compressors are also known which have the thrust bearing on a radially outer location of the forward face of the base of the orbiting scroll member. Such an application is typically used when the bias force F is provided to urge the orbiting scroll member  24  upwardly and toward the non-orbiting scroll member. This invention would apply to such arrangements also. 
         [0020]    Although an embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.