Patent Publication Number: US-8118563-B2

Title: Tandem compressor system and method

Description:
FIELD 
     The present disclosure relates to a tandem compressor system and method. 
     BACKGROUND 
     The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
     A tandem compressor system consists of two compressors. A discharge tube assembly connects the two compressors to the outside system. When only a single compressor is running, oil may enter the discharge tube assembly and flow back toward the non-running compressor. The presence of oil in the discharge tube near the non-running compressor adds mass to the discharge tube assembly and reduces tube modal frequencies, which, in turn, may lead to tube resonance problems and tube failures. 
     SUMMARY 
     The present teachings provide a compressor system comprising a first compressor and a second compressor. The first and second compressors may each include a shell, a compression mechanism disposed within the shell, and a drive member adapted to drive the compression mechanism. A discharge tube assembly including a first discharge tube and a second discharge tube may interconnect the first compressor and the second compressor, and a distal portion of the first discharge tube and a distal portion of the second discharge tube may be joined at a common discharge tube. A proximate portion of the first discharge tube may be elevated relative the distal portion of the first discharge tube. 
     The proximate portion may include a shock loop. 
     The proximate portion may be elevated relative to the distal portion to prevent a backflow of oil through the discharge tube assembly. 
     The proximate portion may be angled relative to the distal portion between 5 degrees and 10 degrees. 
     The proximate portion may be angled relative to the distal portion between 1 degree and 90 degrees. 
     The proximate portion may be elevated relative to the distal portion by at least one half a tube diameter. 
     A proximate portion of the second discharge tube may be elevated relative the distal portion of the second discharge tube. 
     The present teachings also provide a compressor system comprising a first compressor and a second compressor. The first and second compressors may each include a shell, a compression mechanism disposed within the shell, a drive member adapted to drive the compression mechanism, a suction inlet fitting, and a discharge fitting. A discharge tube assembly may extend from the discharge fittings including a first discharge tube and a second discharge tube interconnecting the first compressor and the second compressor. A distal portion of the first discharge tube and a distal portion of the second discharge tube may be joined at a common discharge tube, and a proximate portion of the first discharge tube may be elevated relative the discharge fitting of the first compressor. 
     The proximate portion may prevent a backflow of oil through the discharge tube assembly. 
     The proximate portion may be upwardly angled relative the distal portion 
     The proximate portion may be upwardly angled relative the distal portion between 5 degrees and 10 degrees. 
     The proximate portion may be upwardly angled relative the distal portion between 1 degree and 90 degrees. 
     The proximate portion may be elevated relative to the discharge fitting by at least one half a tube diameter. 
     A proximate portion of the second discharge tube may be elevated relative the distal portion of the second discharge tube. 
     The present teachings also provide a compressor system comprising a first compressor and a second compressor. The first and second compressors may each include a shell, a compression mechanism disposed within the shell, and a drive member adapted to drive the compression mechanism. The compression mechanism may include a first scroll member having a first spiral wrap, and a second scroll member having a second spiral wrap intermeshed with the first spiral wrap of the first scroll member. A discharge tube assembly including a first discharge tube and a second discharge tube may interconnect the first compressor and the second compressor. Distal portions of the first and second discharge tubes may be joined at a common discharge tube, and proximate portions of the first and second discharge tubes may be elevated relative the distal portions. 
     The proximate portions may prevent a backflow of oil through the discharge tube assembly. 
     The proximate portions may be upwardly angled relative the distal portions between 5 degrees and 10 degrees. 
     The proximate portion of the first discharge tube may be upwardly angled relative the distal portion of the first discharge tube between 1 degree and 90 degrees. 
     The proximate portions may be elevated relative to the distal portions by at least one half a tube diameter of the first and second discharge tubes. 
     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 claims. 
    
    
     
       DRAWINGS 
       The drawings described herein are for illustration purposes only and are not intended to limit the present disclosure. 
         FIG. 1  is a perspective view of a tandem compressor system including a discharge tube assembly according to the present teachings; 
         FIG. 2  is a cross-sectional view of an exemplary compressor used in the tandem compressor system; 
         FIG. 3  is a perspective view of a prior art discharge tube assembly; 
         FIG. 4  is a perspective view of a discharge tube assembly according to the present teachings; and 
         FIG. 5  is a perspective view of a tandem compressor system including a discharge tube assembly according to the present teachings. 
     
    
    
     DETAILED DESCRIPTION 
     The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. 
     Referring to  FIG. 1 , a compressor system  2  including a tandem compressor configuration  10  is shown. Compressor system  2  generally includes tandem configuration  10 , a condenser  4 , and an evaporator  6 . Tandem configuration  10  includes a pair of compressors  12  and  12 ′ that are adapted to operate either singularly or in combination. Each of compressors  12  and  12 ′ may be a scroll compressor, as illustrated in  FIGS. 1 and 2 , or any other type of compressor known in the art. In this regard, the present teachings may be adapted to operate with any type of compressor known to one skilled in the art, including rotary, rotating, orbiting, and reciprocating types. 
     As shown in  FIG. 2 , compressors  12  and  12 ′ may include a cylindrical hermetic shell  14 , a compression mechanism  16 , a main bearing housing  18 , a motor assembly  20 , a refrigerant discharge fitting  22 , and a suction gas inlet fitting  24 . Hermetic shell  14  may house compression mechanism  16 , main bearing housing  18 , and motor assembly  20 . Shell  14  may include an end cap  26  at an upper end thereof and a transversely extending partition  28 . Refrigerant discharge fitting  22  may be attached to shell  14  at an opening  30  in end cap  26 . Suction gas inlet fitting  24  may be attached to shell  14  at an opening  32 . Compression mechanism  16  may be driven by motor assembly  20  and supported by main bearing housing  18 . Main bearing housing  18  may be affixed to shell  14  at a plurality of points in any desirable manner. 
     Motor assembly  20  may generally include a motor  34 , a frame  36  and a drive member or drive shaft  38 . Motor  34  may include a motor stator  40  and a rotor  42 . Motor stator  40  may be press fit into frame  36 , which may in turn be press fit into shell  14 . Drive shaft  38  may be rotatably driven by stator  40 . Windings  44  may pass through stator  40 . Rotor  42  may be press fit on drive shaft  38 . A motor protector  46  may be provided in close proximity to windings  44  so that motor protector  46  will de-energize motor  34  if windings  44  exceed their normal temperature range. 
     Drive shaft  38  may include an eccentric crank pin  48  having a flat  49  thereon and one or more counter-weights  50  at an upper end  52 . Drive shaft  38  may include a first bearing portion  53  rotatably journaled in a first bearing  54  in main bearing housing  18  and a second bearing portion  55  rotatably journaled in a second bearing  56  in frame  36 . Drive shaft  38  may include an oil-pumping concentric bore  58  at a lower end  60 . Concentric bore  58  may communicate with a radially outwardly inclined and relatively smaller diameter bore  62  extending to the upper end  52  of drive shaft  38 . The lower interior portion of shell  14  may be filled with lubricating oil. Concentric bore  58  may provide pump action in conjunction with bore  62  to distribute lubricating fluid to various portions of compressor  12  and  12 ′. 
     Compression mechanism  16  may generally include an orbiting scroll  64  and a non-orbiting scroll  66 . Orbiting scroll  64  may include an end plate  68  having a spiral vane or wrap  70  on the upper surface thereof and an annular flat thrust surface  72  on a lower surface. Thrust surface  72  may interface with an annular flat thrust bearing surface  74  on an upper surface of main bearing housing  18 . A cylindrical hub  76  may project downwardly from thrust surface  72  and may include a journal bearing  78  having a drive bushing  80  rotatively disposed therein. Drive bushing  80  may include an inner bore in which crank pin  48  is drivingly disposed. Crank pin flat  49  may drivingly engage a flat surface in a portion of the inner bore of drive bushing  80  to provide a radially compliant driving arrangement. 
     Non-orbiting scroll member  66  may include an end plate  82  having a non-orbiting spiral wrap  84  on lower surface  86  thereof. Non-orbiting spiral wrap  84  may form a meshing engagement with wrap  70  of orbiting scroll member  64 , thereby creating an inlet pocket  88 , intermediate pockets  90 ,  92 ,  94 ,  96 , and outlet pocket  98 . Non-orbiting scroll  66  may have a centrally disposed discharge passageway  100  in communication with outlet pocket  98  and upwardly open recess  102  which may be in fluid communication via an opening  103  in partition  28  with a discharge muffler chamber  104  defined by end cap  26  and partition  28 . 
     Non-orbiting scroll member  66  has in the upper surface thereof an annular recess  105  having parallel coaxial side walls in which is sealingly disposed for relative axial movement an annular floating seal  107  which serves to isolate the bottom of recess  105  from the presence of gas under suction and discharge pressure so that it can be placed in fluid communication with a source of intermediate fluid pressure by means of a passageway  109 . A spring  111  may urge floating seal  107  upward to maintain a sealing engagement. Non-orbiting scroll member  66  is thus axially biased against orbiting scroll member  64  by the forces created by discharge pressure acting on the central portion of scroll member  66  and those created by intermediate fluid pressure acting on the bottom of recess  105 . 
     Compressor  12  and  12 ′ may use a dual pressure balancing scheme to axially balance non-orbiting scroll member  66  with floating seal  107  being used to separate the discharge gas pressure from the suction gas pressure. 
     A solenoid valve  113  may be used to open and close a passageway  115  located within non-orbiting scroll  66 . Passageway  115  extends from the bottom of recess  105  which is at intermediate pressure during operation of compressor  12  and  12 ′ to the area of compressor  12  and  12 ′ which contains suction gas at suction gas pressure. 
     Relative rotation of the scroll members  64  and  66  may be prevented by an Oldham coupling, which may generally include a ring  108  having a first pair of keys  110  (one of which is shown) slidably disposed in diametrically opposed slots  112  (one of which is shown) in non-orbiting scroll  66  and a second pair of keys (not shown) slidably disposed in diametrically opposed slots in orbiting scroll  64 . 
     As stated earlier it should be understood that although the above scroll compressor  12  and  12 ′ may be used for each compressor in the tandem compressor configuration  10 , any type of scroll compressor may be used for the compressors  12  and  12 ′ that is known to one skilled in the art. Moreover, although it is preferred that the same type of compressor be used for each compressor in tandem configuration  10 , it is not out of the scope of the present teachings to use different types of scroll compressors for each of the compressors. Also, although the compressors  12  and  12 ′ are shown to stand vertically in  FIG. 1 , the present teachings should not be limited thereto. The compressors  12  and  12 ′, rather, may also be horizontally oriented so long as the backflow of oil through a discharge tube assembly is prevented, as described below. 
     Compressors  12  and  12 ′ are connected by a refrigerant tube  8  that enables a refrigerant or fluid to pass between each of compressors  12  and  12 ′. In this manner, compressors  12  and  12 ′, when operating in tandem, may operate with an increased output capacity. In accordance with the present teaching, compressors  12  and  12 ′ also share a discharge tube assembly  114  that connects compressors  12  and ′ 12 , as well as connects compressors  12  and  12 ′ to refrigerant system  2  including condenser  4  and evaporator  6 . Discharge tube assembly  114  shared by the compressors  12  and  12 ′ is shown, for example, in  FIG. 1 . 
     With particular reference to  FIGS. 3 and 4 , discharge tube assembly  114  includes a pair of proximate portions  116  and  116 ′ that are connected to outlet fittings  22  of compressors  12  and  12 ′. Proximate portion  116 ′ connected to compressor  12 ′ may include a shock loop  118 , which may be used to reduce stress in discharge tube assembly  114  during start/stop and running conditions by changing a stiffness of the discharge tube assembly  114  and its resonant frequencies. After shock loop  118 , proximate portions  116  and  116 ′ of compressors  12  and  12 ′ connect to elongated tubes  120  and  120 ′. Elongated tubes  120  and  120 ′ connect to a common discharge tube  121  at distal ends  123  thereof via a fitting  125  ( FIG. 1 ). Common discharge tube  121  connects compressors  12  and  12 ′ to the rest of compressor system  2 , which includes condenser  4  and evaporator  6 . 
       FIG. 3  shows a conventional discharge tube assembly  130  including a shock loop  118 . As shown in  FIG. 3 , after shock loop  118 , proximate portions  132  and  134  of compressors  12  and  12 ′ each connect to elongated tubes  136  and  138  that are substantially straight and horizontal. When only compressor  12  of the tandem configuration  10  is running, oil may pass through the proximate portion  132 , enter elongated tube  136 , and subsequently enter common discharge tube  121 . Because elongated tubes  136  and  138  are substantially straight and horizontal, the oil that has entered common discharge tube  121  may flow back towards and reenter elongated tubes  136  and  138 . If oil enters elongated tube  138 , oil may subsequently accumulate in shock loop  118  of proximate portion  134  adjacent compressor  12 ′. Any oil that accumulates in shock loop  118  may add unnecessary mass to discharge tube assembly  130  and may reduce the modal frequencies of discharge tube assembly  130 . The reduced modal frequencies may lead to resonant problems of the discharge tube assembly  130 , which in turn may lead to the assembly  130  failing. That is, discharge tube assembly  130  may break off from outlet fittings  22  of compressors  12  and  12 ′. 
     Discharge tube assembly  114  shown in  FIG. 4  may be provided with an inclined portion  122 , which prevents, or at least minimizes, any oil that may accumulate in elongated tube  120 ′ from flowing into shock loop  118 . Inclined portion  122  elevates proximate portion  116 ′ relative to distal portion  123  of elongated tube  120 ′ and discharge fitting  22 , and requires any oil present in the elongated tube  120 ′ to flow upwards through inclined portion  122  before it can reach shock loop  118 . Due to gravity, the oil is prevented from flowing through inclined portion  122  into shock loop  118 . Modal frequencies of discharge tube assembly  114 , therefore, may be controlled and failure of discharge tube assembly  114  may be prevented. 
     Inclined portion  122  may be angled upward relative elongated tube  120 ′ by an angle between 5 degrees and 10 degrees relative horizontal. Inclined portion  122  may be formed by bending discharge tube assembly  114  at a point adjacent shock loop  118 , which may reduce manufacturing time and cost. Notwithstanding, any angle of inclination between about 1 degree and 90 degrees relative horizontal may be used. 
     Discharge tube assembly  114 ′ in  FIG. 5  has an inclined portion  126  inclined approximately 80 degrees to 90 degrees relative to horizontal tube  120 ′. Inclined portion  126  may also be elevated relative to horizontal tube  120 ′ and discharge fitting  22  by a distance that may range between half a diameter of tube  120 ′ and a diameter of tube  120 ′. In other words, the distance between inclined portion  126  and elongated tube  120 ′ may range between a half diameter of tube  120 ′ and a full diameter of tube  120 ′. Regardless, inclined portion  126  may be elevated relative to elongated tube  120 ′ that is sufficient to prevent backflow of oil. 
     Furthermore, it should be understood that although the present teachings have been described relative to a discharge tube assembly  114  including shock loop  118 , the present teachings should not be limited thereto. That is, discharge tube assembly  114  does not require use of shock loop  118  and may be formed to have an inclined portion  122  formed near proximate portion  116 ′ of discharge tube assembly  114  adjacent outlet fitting  22  of the compressor  12 ′. Moreover, each compressor  12  and  12 ′ may include a proximate portion  116  and  116 ′ that includes an inclined portion  122  and  122 ′ relative to horizontal tube  120 . 
     The description of the present teachings is merely exemplary in nature and, thus, variations that do not depart from the gist of the present teachings are intended to be within the scope of the present teachings. Such variations are not to be regarded as a departure from the spirit and scope of the present teachings.