Abstract:
A scroll compressor comprises a first scroll member having a generally spiral wrap and a second scroll member having a generally spiral wrap. The generally spiral wraps interfit to define compression chambers. A pair of ports leads from the compression chambers. A pair of valves selectively blocks flow of refrigerant from the ports leaving the compression chambers. The valves selectively control the flow such that flow may pass from neither of the two ports, from both of the two ports, or from only one of the two ports to provide three levels of capacity control.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This application relates to a scroll compressor having capacity control valving. 
         [0002]    Scroll compressors are becoming widely utilized in refrigerant compression applications. In a typical scroll compressor, a first generally spiral scroll wrap interfits with a second generally spiral scroll wrap. The interfitting wraps define compression chambers that entrap and compress a refrigerant. 
         [0003]    Under various conditions in refrigerant compression applications, it may be desirable to reduce the capacity, or amount of refrigerant that is being compressed. As an example, should the load on an air conditioning system drop, then it would be energy efficient to reduce the amount of refrigerant compressed. Various types of capacity control are known. In one standard capacity control, valves open ports that communicate the compression chambers back to a suction chamber in the scroll compressor. When the valves are open, the refrigerant flows back to the suction chamber, and the amount of refrigerant that is fully compressed is reduced, thereby reducing the capacity, and the energy used by the compressor. 
         [0004]    Various capacity control arrangements are known and have been used, however, in general, they have not provided as much flexibility as would be desirable. 
       SUMMARY OF THE INVENTION 
       [0005]    In a disclosed embodiment of this invention, a scroll compressor is provided with three steps of capacity control. 
         [0006]    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 
         [0007]      FIG. 1  schematically shows a scroll compressor. 
           [0008]      FIG. 2  is a flow schematic of a first embodiment of this invention. 
           [0009]      FIG. 3  shows a second embodiment. 
           [0010]      FIG. 4  shows a third embodiment. 
           [0011]      FIG. 5  shows yet another embodiment. 
           [0012]      FIG. 6  shows another embodiment. 
           [0013]      FIG. 7  shows another feature of the  FIG. 6  embodiment. 
           [0014]      FIG. 8  shows another embodiment. 
           [0015]      FIG. 9A  shows yet another embodiment. 
           [0016]      FIG. 9B  shows another portion of the  FIG. 9A  embodiment. 
           [0017]      FIG. 9C  shows another portion of the  FIG. 9A  embodiment. 
           [0018]      FIG. 9D  shows yet another portion of the  FIG. 9A  embodiment. 
           [0019]      FIG. 10  shows yet another embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0020]    A scroll compressor  20  as illustrated in  FIG. 1  includes an orbiting scroll member  22  interfitting with a non-orbiting scroll member  24 . Compression chambers  26  are defined between the scroll members  22  and  24 . As shown in this Figure, the wrap on the scroll members includes a first outer higher portion  10  and an inner lower portion  11 . Such two-step scroll compressors are known, and are disclosed for example in co-pending patent application Ser. No. 11/833,342, entitled Stepped Scroll Compressor With Staged Capacity Modulation. 
         [0021]    The compression chambers  26  are shown communicating with ports  28  and  30 . Valves  32  and  36  are shown schematically, and can selectively communicate the ports  28  and  30  back to a suction pressure chamber  38  through passages  36 . Typically, when operating at full capacity, the orbiting scroll member  28  is driven to orbit by a motor  12 , and compresses the refrigerant in the compression chambers  26  toward a discharge port  40 . Refrigerant compressed through the discharge port  40  passes into a discharge pressure chamber  42 , and then to a downstream use. However, when less capacity is necessary, one or both of the valves  32  and  34  may be opened to reduce the provided capacity. In this manner, three steps of capacity can be provided, e.g., 100%, 70%, and 45% of capacity. 
         [0022]      FIG. 2  shows a first schematic  60  wherein a single solenoid valve  62  includes a blocking portion  64 , a portion  66 , and another portion  68 . A source of pressurized gas  78 , which may be from the discharge pressure chamber  42 , communicates to the valve  62 . Voltage is selectively applied to solenoid  70  to properly position the valve  62 . In the illustrated position, the source of pressurized gas  72  does not communicate to either line  80  or  82 . Lines  80  and  82  provide pressurized fluid to valves  72  and  74 . The valves  72  and  74  are typically moved by a spring to a position allowing the flow of refrigerant from the pockets  28  and  30  back to the suction chamber  38 . Of course, the valves  72  and  74  can be normally positioned such that they block flow. 
         [0023]    When full capacity is desired, then the valve  62  is moved to the position such that the source  78  is aligned with the portion  66 . Pressurized refrigerant now flows to both lines  80  and  82 , and both valves  72  and  74  are biased to the closed position. When a first step of reduced capacity is desired, the valve is moved such that portion  68  aligns with source  78 . In that position, pressurized refrigerant is sent through the passage  82 , and the valve  74  is biased to a closed position with the valve  72  remaining open. Now, an intermediate reduced capacity is achieved. Again, when even less capacity is desired, the valve  60  is moved back to the illustrated position such that pressurized fluid does not flow to valve  72  or  74 . 
         [0024]      FIG. 3  shows another embodiment  90  wherein the basic arrangement of  FIG. 2  is maintained, however, only two steps of capacity control are used. In this embodiment, the valve  94  has portions  96  and  98 . When in the illustrated position, biased by a spring, the source of pressurized gas  78  does not communicate to the line  92 . Both valves are maintained in their open position and a reduced capacity is achieved. On the other hand, when full capacity is desired, the valve is moved such that portion  96  aligns with the source  78 , and both valves  72  and  74  are moved to block the reduction of capacity. 
         [0025]      FIG. 4  shows yet another embodiment  100  wherein passages  102  selectively communicate to central passages  106  leading back to a suction pressure area in the scroll compressor. Additional passages may be necessary to fully communicate portion  106  to a suction portion. Valves  108  and  110  may be solenoid valves, and may be left in the illustrated position to reduce capacity. When full capacity is desired, the valves are moved to block flow from the passage  102  reaching the passage  106 . In addition, only one of the two valves may be opened to provide an intermediate capacity reduction. 
         [0026]      FIG. 5  shows yet another embodiment  120  wherein the valves  108  and  110  block flow from a point  122  from reaching a passage  124  leading back to the suction pressure chamber. Again, three steps of capacity can be provided by the  FIG. 5  embodiment by either blocking both passages  122 , allowing flow through both, or blocking only one. 
         [0027]      FIG. 6  shows an embodiment  151  wherein a rotary plate  152  is driven by a motor  153 . As shown in  FIG. 7 , the plate  152  has a first position  154  wherein one of the two passages such as shown in the prior embodiments is allowed to dump to the suction chamber. A second position  156  aligns both passages with the suction chamber. A third position  155  will block flow from both passages. 
         [0028]      FIG. 8  shows yet another embodiment  159  wherein a rotary motor  160  has a rotary to linear connection of some sort that drives an elongate rod  166  to either block or allow flow from the passages  162  and  164 . 
         [0029]      FIG. 9A  shows another embodiment wherein a motor  182  drives a rotary valve  180 . The rotary valve  180  selectively communicates the two passages  190  and  192  communicating with the compression chambers to dump passages  194  and  196  leading back to suction. As shown in  FIG. 9B , in one position of the valve  180 , a head  184  includes two passages  186 . When these passages are aligned with the passages  190  and  192 , then flow is dumped from both passages, and a greatest amount of capacity reduction is achieved. 
         [0030]      FIG. 9C  shows the head  180  in another position  184  wherein only one passage  191  communicates with the passage  190 . This will provide an intermediate amount of capacity reduction. 
         [0031]      FIG. 9D  shows another position  193  wherein flow from both passages  190  and  192  will be blocked. 
         [0032]      FIG. 10  shows yet another embodiment  170  wherein a rotary gear  171  rotates rack teeth on a ring  172 . Ports  174  and  176  can be selectively opened or closed by properly rotating the rack  172 . 
         [0033]    Several embodiments of this invention have 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.