Patent Publication Number: US-6655172-B2

Title: Scroll compressor with vapor injection

Description:
FIELD OF THE INVENTION 
     The present invention relates to scroll type machines. More particularly, the present invention relates to hermetic scroll compressors incorporating a vapor injection system which utilizes a heat exchanger or a flash tank which is mounted directly to the shell of the scroll compressor. 
     BACKGROUND AND SUMMARY OF THE INVENTION 
     Refrigeration and air conditioning systems typically include a compressor, a condenser, an expansion valve or equivalent and an evaporator. These components are coupled in sequence in a continuous serial flow path. A working fluid or refrigerant flows through the system and alternates between a liquid phase and a vapor or gaseous phase. 
     A variety of compressor types have been used in refrigeration and air conditioning systems, including but not limited to reciprocating compressors, screw compressors and rotary compressors. Rotary compressors can include both the vane type compressors as well as the scroll machines. Scroll machines are constructed using two scroll members with each scroll member having an end plate and a spiral wrap extending generally perpendicular to the respective end wrap. The spiral wraps are arranged in an opposing manner with the two spiral wraps being interleaved or interfitted with each other. The scroll members are mounted so that they may engage in relative orbiting motion with respect to each other. During this orbiting movement, the spiral wraps define a successive series of enclosed pockets or spaces, each of which progressively decreases in size as it moves inwardly from a radially outer position at a relatively low suction pressure to a central position at a relatively higher or discharge pressure. The compressed fluid exits from the enclosed space at the central position through a discharge passage formed through the end plate of one of the scroll members. 
     Refrigeration and air conditioning systems are now incorporating vapor injection systems where a portion of the refrigerant in gaseous form is injected into the enclosed pockets or spaces at a pressure which is intermediate the low suction pressure and the relatively high discharge pressure. This gaseous refrigerant is injected into the enclosed pockets or spaces through one or more injection ports which extend through one of the two scroll members. The injection of this gaseous refrigerant has the effect of increasing both the refrigeration or air conditioning system&#39;s capacity and the efficiency of the refrigeration or air conditioning system. In refrigeration or air conditioning systems where vapor injection is incorporated to achieve maximum capacity and maximum efficiency increases, the development engineer attempts to provide an injection system which will maximize the amount of refrigerant gas that is injected into the enclosed pocket as well as maximizing the intermediate pressure at which the refrigerant gas is injected into the enclosed pocket. By maximizing both the amount of refrigerant gas as well as the pressure of the refrigerant gas that is injected, the system capacity and the system efficiency of the refrigeration or air conditioning system are maximized. 
     When developing the vapor injection system, the development engineer must consider the source for the vapor that is injected into the pockets. Typically, the vapor refrigerant source is through a connection at a position within the refrigeration circuit and a device such as a flash tank or an economizer is utilized to separate vapor refrigerant from gaseous refrigerant to ensure that only gaseous or vapor refrigerant is injected into the enclosed pockets or spaces. When accessing liquid refrigerant from a position within the refrigeration circuit, the vapor or gaseous refrigerant is typically piped to the compressor through a fluid line which extends between the position within the refrigeration circuit and the compressor. The use of fluid piping between the source of vapor or gaseous refrigerant and the compressor provides a system where pressure drop of the gaseous refrigerant can occur due to fluid line losses and/or temperature loses. While it is possible to insulate this line in order to limit temperature losses, this insulation adds additional cost and complexity to the refrigerant or air-conditioning system as well as presenting problems during the servicing of the system. 
     Thus, the continued development of vapor injection systems is directed towards increasing the amount and pressure of intermediate pressurized vapor that can be injected into the enclosed spaces. 
     The present invention provides the art with a vapor injection system where a flash tank, an economizer or a heat exchanger is mounted directly to the hermetic shell of the compressor. The direct attachment of the flash tank, the economizer or the heat exchanger eliminates all external tubing required for the intermediate pressurized gaseous refrigerant. The direct attachment of the flash tank, the economizer or the heat exchanger provides the advantages of a more compact single unit, there is less pressure drop, the installation is easier, it is not necessary to isolate or insulate the vapor injection fluid line, there are fewer components that need to be connected during installation and the refrigeration or air conditioning system will be lower in cost. 
     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 
     The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
     FIG. 1 is a vertical cross-section of a scroll compressor in accordance with the present invention; 
     FIG. 2 is a horizontal sectional view of the scroll compressor shown in FIG. 1 taken just below the partition plate; 
     FIG. 3 is a vertical side view of the scroll compressor shown in FIG. 1 with an attached flash tank in accordance with the present invention; 
     FIG. 4 is a schematic illustration of a heat exchanger utilized with a vapor injection system of a refrigeration system in accordance with another embodiment of the present invention; 
     FIG. 5 is a vertical side view of the scroll compressor shown in FIG. 1 in conjunction with a heat exchanger in accordance with the schematic illustration shown in FIG. 4; 
     FIG. 6 is a perspective view of the scroll compressor shown in FIG. 1 in conjunction with a heat exchanger in accordance with another embodiment of the present invention; and 
     FIG. 7 is a vertical side view of the scroll compressor shown in FIG. 5 in conjunction with a heat exchanger and an inverter in accordance with another embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. 
     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 which is designed to accommodate the unique vapor injection systems in accordance with the present invention and which is designated generally by the reference numeral  10 . The following description of the preferred embodiment is merely exemplary in nature and is no way intended to limit the invention, its application or its uses. 
     Scroll 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  which may have the usual discharge valve therein (not shown). Other major elements affixed to shell  12  include a transversely extending partition  20  which is welded about its periphery at the same point cap  14  is welded to shell  12 , an inlet fitting  22 , a main bearing housing  24  which is suitably secured to shell  12  and a lower bearing housing  26  having a plurality of radially outwardly extending legs each of which is suitably secured to shell  12 . A motor stator  28  which is generally square in cross-section but with the corners rounded off is press fit into shell  12 . The flats between the rounded corners on motor stator  28  provide passageways between motor stator  28  and shell  12  which facilitate the return flow of the lubricant from the top of shell  12  to its bottom. 
     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 in a bearing  36  in lower bearing housing  26 . Crankshaft  30  has at the lower end thereof a relatively large diameter concentric bore  38  which communicates with a radially outwardly located smaller diameter bore  40  extending upwardly therefrom to the top of crankshaft  30 . Disposed within bore  38  is a stirrer  42 . The lower portion of the interior shell  12  is filled with lubricating oil and bores  38  and  40  act as a pump to pump the lubricating oil up crankshaft  30  and ultimately to all of the various portions of scroll compressor  10  which require lubrication. 
     Crankshaft  30  is relatively driven by an electric motor which includes motor stator  28  having motor windings  44  passing therethrough and a motor rotor  46  press fitted onto crankshaft  30  and having upper and lower counterweights  48  and  50 , respectively. A motor protector  52 , of the usual type, is provided in close proximity to motor windings  44  so that if the motor exceeds its normal temperature range, motor protector  52  will de-energize the motor. 
     The upper surface of main bearing housing  24  is provided with an annular flat thrust bearing surface  54  on which is disposed an orbiting scroll member  56 . Scroll member  56  comprises an end plate  58  having the usual spiral valve or wrap  60  on the upper surface thereof and an annular flat thrust surface  62  on the lower surface thereof. Projecting downwardly from the lower surface is a cylindrical hub  64  having a journal bearing  66  therein and in which is rotatively disposed a drive bushing  68  having an inner bore within which crank pin  32  is drivingly disposed. Crank pin  32  has a flat on one surface (not shown) which drivingly engages a flat surface in a portion of the inner bore of drive bushing  68  to provide a radially compliant drive arrangement such as shown in assignee&#39;s U.S. Pat. No. 4,877,382, the disclosure of which is incorporated herein by reference. 
     Wrap  60  meshes with a non-orbiting scroll wrap  72  forming part of a non-orbiting scroll member  74 . During orbital movement of orbiting scroll member  56  with respect to non-orbiting scroll member  74  creates moving pockets of fluid which are compressed as the pocket moves from a radially outer position to a central position of scroll members  56  and  74 . Non-orbiting scroll member  74  is mounted to main bearing housing  24  in any desired manner which will provide limited axial movement of non-orbiting scroll member  74 . The specific manner of such mounting is not critical to the present invention. 
     Non-orbiting scroll member  74  has a centrally disposed discharge port  76  which is in fluid communication via an opening  78  in partition  20  with a discharge muffler  80  defined by cap  14  and partition  20 . Fluid compressed by the moving pockets between scroll wraps  60  and  72  discharges into discharge muffler  80  through port  76  and opening  78 . Non-orbiting scroll member  74  has in the upper surface thereof an annular recess  82  having parallel coaxial sidewalls within which is sealing disposed for relative axial movement an annular seal assembly  84  which serves to isolate the bottom of recess  82  so that it can be placed in fluid communication with a source of intermediate fluid pressure by means of a passageway  86 . Non-orbiting scroll member  74  is thus axially biased against orbiting scroll member  56  by the forces created by discharge pressure acting on the central portion of non-orbiting scroll member  74  and the forces created by intermediate fluid pressure acting on the bottom of recess  82 . This axial pressure biasing, as well as the various techniques for supporting non-orbiting scroll member  74  for limited axial movement, are disclosed in much greater detail in assignee&#39;s aforementioned U.S. Pat. No. 4,877,382. 
     Relative rotation of scroll members  56  and  74  is prevented by the usual Oldham Coupling  88  having a pair of key slidably disposed in diametrically opposing slots in non-orbiting scroll member  74  and a second pair of keys slidably disposed in diametrically opposed slots in orbiting scroll member  56 . 
     Scroll compressor  10  is preferably of the “low side” type in which suction gas entering shell  12  is allowed, in part, to assist in cooling the motor. So long as there is an adequate flow of returning suction gas, the motor will remain within the desired temperature limits. When this flow ceases, however, the loss of cooling will cause motor protector  52  to trip and shut scroll compressor  10  down. 
     The scroll compressor, as thus broadly described, is either known in the art or it is the subject matter of other pending applications for patent by Applicant&#39;s assignee. The details of construction which incorporate the principles of the present invention are those which deal with a unique vapor injection system identified generally by reference numeral  100 . Vapor injection system  100  is used to inject vapor or gaseous refrigerant for increasing the capacity and efficiency of scroll compressor  10 . 
     Referring now to FIGS. 1-3, vapor injection system  100  comprises a vapor injection passage  102  extending through an end plate  90  of non-orbiting scroll member  74 , a single vapor injection port  104  opening into the enclosed fluid pockets, a connecting tube  106 , a fluid injection port  108  extending through shell  12  to the outside of shell  12 . 
     Vapor injection passage  102  is a cross drill feed hole which extends generally horizontal through non-orbiting scroll member  74  from a position on the exterior of non-orbiting scroll member  74  to a position where it communicates with vapor injection port  104 . Vapor injection port  104  extends generally vertically from passage  102  through non-orbiting scroll member  74  to open into the enclosed spaces or pockets formed by wraps  60  and  72 . Connecting tube  106  extends from vapor injection passage  102  to fluid injection port  108  where it sealingly secures to fluid injection port  108  which is in turn connected to either the flash tank or the heat exchanger of the refrigeration systems described below. 
     Referring now to FIG. 3, scroll compressor  10  is shown assembled as part of a refrigeration system  120 . Refrigeration system  120  comprises scroll compressor  10 , a condenser  122 , a first expansion device in the form of an expansion valve or fixed orifice  124 , a flash tank  126 , a second expansion device in the form of an expansion valve  128  and an evaporator  130 . 
     In operation, refrigerant compressed by scroll compressor  10  flows through a fluid line to condenser  122  where the refrigerant is cooled and condensed by removing the heat therefrom. From condenser  122 , the liquid refrigerant flows through expansion valve or fixed orifice  124 . Expansion valve or fixed orifice  124  reduces the pressure of the refrigerant. From expansion valve or fixed orifice  124 , the refrigerant flows to flash tank  126 . In flash tank  126 , a part of the refrigerant is evaporated due to the decreased pressure, taking the evaporation heat from the remaining liquid refrigerant gathered in the bottom of flash tank  126 . This sub-cooled liquid refrigerant from flash tank  126  flows through expansion valve  128  and then through evaporator  130  where it is evaporated by taking up heat. The evaporated refrigerant then flows to the suction chamber of scroll compressor  10  where it will be recompressed and the cycle continues. The flashed or gaseous refrigerant generated in flash tank  126  is routed directed through injection port  108  which extends through shell  12 . As described above, connecting tube  106  which is sealingly secured to injection port  108  extends to vapor injection passage  102  which communicates with vapor injection port  104  which opens into one or more of the enclosed spaces defined by scroll wraps  60  and  72 . The sub-cooling of the liquid refrigerant in flash tank  126  attained by the above system prior to reaching evaporator  130  increases the refrigeration capacity of evaporator  130  (i.e., a larger enthalapy difference across evaporator  130  is available). 
     Referring now to FIGS. 4 and 5, scroll compressor  10  is shown as part of a refrigeration system  220 . Refrigeration system  220  comprises scroll compressor  10 , a condenser  222 , a first expansion device in the form of an expansion valve or fixed orifice  224 , a heat exchanger  226 , a second expansion device in the form of an expansion valve  228  and an evaporator  230 . 
     In operation, refrigerant compressed by scroll compressor  10  flows through a fluid line to condenser  222  where the refrigerant is cooled and condensed by removing the heat therefrom. From condenser  222 , the liquid refrigerant flows into heat exchanger  226  through a port  232  and also through expansion valve or fixed orifice  224 . Expansion valve or fixed orifice  224  reduces the pressure and the temperature of the refrigerant which then reverts back to the gaseous stage. This vaporized refrigerant flows into heat exchanger  226  through a port  234  where it removes additional heat from the liquid refrigerant to sub-cool the liquid refrigerant which was supplied to heat exchanger  226  directly from condenser  222  through port  232 . The gaseous refrigerant leaves heat exchanger  226  through a port  236  and is routed directly through injection port  108  which extends through shell  12 . As described above, connecting tube  106  which is sealingly secured to injection port  108  extends to vapor injection passage  102  which communicates with vapor injection port  104  which opens into one or more of the enclosed spaces defined by scroll members  60  and  72 . 
     The sub-cooled liquid refrigerant leaves heat exchanger  226  through a port  238  and flows through expansion valve  228  and then through evaporator  230  where it is evaporated by taking up heat. The evaporated refrigerant then flows to the suction chamber of scroll compressor  10  where it will be recompressed and the cycle continues. The sub-cooling of the liquid refrigerant in heat exchanger  226  attained by the above system prior to reaching evaporator  230  increases the refrigeration capacity of evaporator  230  (i.e., a larger enthalapy difference across evaporator  130  is available). 
     Referring now to FIG. 6, scroll compressor  10  is shown in conjunction with a heat exchanger  326 . Heat exchanger  326  is designed to be placed below scroll compressor  10  within base  16 . Base  16  is increased in height using a circular flange  340  to provide space for bottom mounted heat exchanger  326 . Heat exchanger  326  includes port  232  from condenser  222 , expansion valve or fixed orifice  224  is internal to heat exchanger  326  as well as port  234 . Injection port  108  is repositioned to extend through base  16  rather than shell  12  and heat exchanger  326  includes an internal port  236  which mates with injection port  108  extending through base  16 . Connecting tube  106  would be reconfigured to mate with injection port  108 . Heat exchanger  326  also includes port  238  which is utilized to route the sub-cooled liquid refrigerant to evaporator  230 . The operation, function and advantages described above for refrigeration system  220  with heat exchanger  226  are the same for refrigeration system  220  equipped with heat exchanger  326  in place of heat exchanger  226 . 
     Referring now to FIG. 7, scroll compressor  10  is shown with refrigeration system  220  including condenser  222 , expansion valve or fixed orifice  224 , heat exchanger  226 , expansion valve  228 , evaporator  230  and an inverter  400  mounted on an exterior cooling plate of heat exchanger  226 . Thus, FIG. 7 is the same as FIG. 5 with the addition of inverter  400 . 
     Inverter  400  is in electrical communication with scroll compressor  10  through a power line  402 . Inverter  400  includes an input terminal  404  which is connected to the source of electrical power that powers inverter  400  and thus scroll compressor  10 . During the operation of inverter  400 , a significant amount of heat is generated. The capacity of heat exchanger  326  is sufficient to both cool inverter  400  and the liquid refrigerant using the gaseous refrigerant passing through heat exchanger  326 . The operation, function and advantages for refrigeration system  220  which includes inverter  400  are the same as those disclosed above for refrigeration system  220  without inverter  400 . 
     All of the above described systems provide the advantages that there is no external vapor injection line. This provides a compact single unit for the compressor and the source of fluid, it reduces the pressure drop of the fluid, it simplifies installation, it eliminates isolation of the vapor injection line, it lessens the number of connections required for installation and it reduces the cost of the system. In addition, the above described systems permit the first expansion device  124 ,  224  to be an electronic expansion valve, a thermal expansion valve or a fixed orifice. 
     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.