Patent Publication Number: US-6658866-B2

Title: Scroll expressor

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to a scroll expresser for use in a refrigeration system. 
     Scroll compressors are utilized in many refrigerant systems. After compression of a refrigerant in the scroll compressor to a high pressure, the refrigerant is cooled in a condenser and expanded to a low pressure in an expansion device. After heating of the refrigerant in an evaporator, the refrigerant again enters the scroll compressor, completing the cycle. 
     Scroll compressors include two opposed interfitting scroll plates each having a base and a generally spiral wrap extending from the base. The opposed scroll members define compression chambers. One of the two scroll members is driven to orbit relative to the other by a shaft. As the wraps orbit, refrigerant in the compression chambers are reduced in volume, increasing the pressure of the refrigerant. 
     It is desirable to increase efficiency of a refrigeration system. In all phase changing refrigeration systems, energy is lost at the expansion valve. It would be desirable to employ a refrigeration system with a device in place of an expansion valve which utilizes or recovers the energy of the expansion process in a more efficient manner. 
     SUMMARY OF THE INVENTION 
     The refrigerant system of the present invention employs a scroll expressor in place of an expansion valve. A non-orbiting expander scroll plate and an orbiting expander scroll plate form a plurality of expansion chambers. A non-orbiting compressor scroll plate and an orbiting compressor scroll plate form a plurality of compression chambers. The orbiting compressor scroll plate is keyed to the orbiting expander scroll plate such that the orbiting scroll plates move in the same direction and at the same speed. The orbiting scroll plates move by an off-center crank piece. As the center of mass of the crank piece and the orbiting scroll is not centered, a counter weight is employed to balance the radial inertial force due to the uncentered mass and prevent radial loading. 
     Refrigerant enters the expansion chambers through a high pressure refrigerant inlet. In the expansion chambers, the high pressure refrigerant is expanded to a mixture of low pressure vapor refrigerant and liquid refrigerant. The expanded liquid refrigerant exits the scroll expresser through a low pressure discharge. The low pressure vapor refrigerant flows into the compression chambers for compression. Any excess vapor not ingested by the compressor exits the expressor through the low pressure discharge. A separation element prevents passage of the liquid refrigerant into the compression chambers. After compression of the vapor refrigerant in the compression chambers, the refrigerant is discharged through a high pressure vapor discharge and mixes with refrigerant exiting the system compressor which is connected to the scroll expressor in parallel. Preferably, the volume ratio of the expansion chambers is greater than the volume ratio of the compression chambers. 
     A spring positioned between the orbiting expander scroll plate and the orbiting compressor scroll plate reduces both axial loading and axial clearance in the scroll expresser. The spring counteracts the tendency of the high pressure gases in the compression chambers to separate the orbiting compressor scroll plate from the non-orbiting compressor scroll plate. The spring also counteracts any gaps which may form due to wearing of the scroll plates and cause leakage. 
     Alternatively, the orbiting scroll plates may be integrated into one component. A drive mechanism with a combined crank piece and counterweight guides the orbiting scroll plate to cause expansion and compression of the refrigerant. 
     These and other features of the present invention will be best understood from the following specification and drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The various features and advantages of the invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows: 
     FIG. 1 illustrates a schematic diagram of a prior art refrigerant system; 
     FIG. 2 illustrates a schematic diagram of the refrigerant system of the present invention employing a scroll expresser; 
     FIG. 3 illustrates the scroll expresser of the present invention; 
     FIG. 4 illustrates a cross sectional view of the scroll expressor of FIG. 3 taken along lines  4 — 4  showing the orbiting of the expansion scrolls; 
     FIG. 5 illustrates a cross sectional view of the scroll expressor of FIG. 3 taken along lines  5 — 5  showing the orbiting of the compressor scrolls; 
     FIG. 6 illustrates a cross sectional view of the scroll expresser of FIG. 3 taken along lines  6 — 6  showing the crank piece and the shaft; and 
     FIG. 7 illustrates an alternative scroll expresser of the present invention taken along line  7 — 7  of FIG. 8; and 
     FIG. 8 illustrates a top view of the scroll expressor of FIG.  7 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 illustrates a schematic diagram of a prior art refrigerant system  10  including a compressor  12 , a condenser  14 , an expansion device  16 , and an evaporator  18 . After refrigerant vapor exits the compressor  12  at high pressure and enthalpy, the refrigerant flows through the condenser  14  where the refrigerant condenses into a liquid, exiting at low enthalpy and high pressure. The liquid refrigerant is then expanded to a low pressure liquid-vapor mixture in the expansion device  16  followed by heating in the evaporator  18 . The refrigerant exits the evaporator  18  generally as a vapor at low pressure and intermediate enthalpy. The vapor refrigerant is then compressed in the compressor  12 , completing the cycle  10 . 
     FIG. 2 illustrates a schematic diagram of a refrigeration system  20  employing the scroll expressor  26  of the present invention. The system  20  includes a system compressor  22 , a condenser  24 , the scroll expresser  26 , and an evaporator  28 . Refrigerant circulates through the closed circuit system  20 . After refrigerant exits the system compressor  22  at high pressure and enthalpy, refrigerant is cooled and condensed in the condenser  24 , exiting at low enthalpy and high pressure. It is to be understood that system compressor  22  can be any type of compressor. The high pressure low enthalpy liquid refrigerant is then expanded to a low pressure in the scroll expresser  26 , producing both liquid refrigerant and vapor refrigerant. The low pressure low enthalpy liquid refrigerant exits the expressor  26  after expansion and is heated and vaporized in the evaporator  28  followed by compression in the system compressor  22 . The low pressure vapor refrigerant exiting the expansion process is at an intermediate enthalpy similar to the vapor refrigerant exiting the evaporator. The low pressure vapor refrigerant is compressed in the scroll expresser  26  and exits as a high pressure high enthalpy vapor through an expressor vapor discharge line  30  which merges with the discharge  31  of the system compressor  22 . The scroll expressor  26  and the system compressor  22  are thus connected in parallel through their respective high pressure discharge lines. 
     FIG. 3 illustrates the scroll expressor  26  of the present invention. The scroll expresser  26  can be utilized in any refrigeration, air conditioning or heat pump system. The scroll expressor  26  includes a non-orbiting expander scroll plate  32  and an orbiting expander scroll plate  34  with a shaft  36  which define a plurality of expansion chambers  48 . The expander scroll plates  32  and  34  each include a base  33  and  35 , respectively, and a generally spiral wrap  37  and  39 , respectively. The scroll expressor  26  further includes a non-orbiting compressor scroll plate  38  and an orbiting compressor scroll plate  40  which define a plurality of compression chambers  54 . The compressor scroll plates  38  and  40  each include a base  41  and  43 , respectively, and a generally spiral wrap  45  and  47 , respectively. The orbiting compressor scroll plate  40  is keyed to the orbiting expresser scroll plate  34  by a key  68 . An Oldham coupling  66  prevents the orbiting expander scroll  34  from rotating. As the orbiting compressor scroll  40  is connected to the orbiting expander scroll  34  by the key  68 , the orbiting compressor scroll  40  is also prevented from rotating. The non-orbiting expander scroll plate  32  and the non-orbiting compressor scroll plate  38  are connected to an expressor body  42  by a dowel pin  44 . 
     Refrigerant is supplied to the expansion chambers  48  through a high pressure refrigerant inlet  46 . The expansion chambers  48  have a height H E  and a volume ratio V E . In the expansion chambers  48 , the refrigerant is expanded to a low pressure liquid refrigerant and a low pressure vapor refrigerant. After expansion of the refrigerant in the expansion chambers to a low pressure, the liquid refrigerant exits the scroll expressor  26  through the low pressure liquid discharge  50  for evaporation in the evaporator  28  followed by compression in the system compressor  22 . A portion of the low pressure vapor refrigerant also exits through the low pressure liquid discharge  50 . However, it is to be understood that a portion of the low pressure vapor refrigerant can exit through a separate low pressure outlet which bypasses the evaporator  24  and returns directly to the system compressor  22  inlet. A separation element  52  prevents passage of the liquid refrigerant into the compression chambers  54  but allows passage of the vapor refrigerant to the plurality of compression chambers  54 . After expansion, the low pressure liquid and vapor expanded refrigerant flows into a first chamber  73  located above the Oldham coupling  66 . The remainder of the low pressure vapor refrigerant flows along path A from the expander outlet chamber  73  through the separation element  52  and to the compressor inlet chamber  75  to the compression chambers  54 . As the separation element  52  prevents the flow of liquid refrigerant through the separation element  52 , the expanded liquid refrigerant exits the scroll expressor  26  through the low pressure liquid outlet  50 . As stated above, a portion of the low pressure vapor refrigerant also exits through the low pressure liquid outlet  50 . The separation element  52  prevents the passage of liquid refrigerant from the expander outlet chamber  73  to the compressor inlet chamber  75 . 
     The low pressure vapor refrigerant is compressed in the compression chambers  54 . After compression, the refrigerant in the compression chambers  54  is discharged through the high pressure vapor discharge  56  and flows along the expressor vapor discharge line  30  to mix at the compressor discharge  31  with the high pressure refrigerant exiting the system compressor  22 . 
     As the liquid refrigerant entering expansion chambers  48  has a much lower specific volume than the vapor refrigerant exiting the compression chambers  54  and the specific volume of the vapor refrigerant exiting the expansion chambers  48  is the same as the vapor refrigerant entering the compression chambers  54 , the volume ratio V C  of the compression chambers  54  is preferably less than the volume ratio V E  of the expansion chambers  48 . Also, as the power generated by the expansion process is generally less than that power required to recompress the total vapor flow exiting the expansion chambers  48 , the height H C  of the compression chambers  54  is generally less than the height H E  of the expansion chambers  48  in order to reduce the compressor inlet volume to an appropriate value below the expander outlet volume. Alternatively, other parameters of the scroll wrap such as pitch, wall thickness, or wrap angles may also be varied between the expander wraps  37  and  39  and the compressor wraps  45  and  47  in order to define a reduced compressor inlet volume. However, it should be understood that preferably the orbiting radius of both sets of wraps  37 ,  39 ,  45 , and  47  should be the same or nearly the same in order that the expander orbiting scroll plate  34  directly drives the compressor orbiting scroll plate  40 . As the height H C  is generally less than the height H E , a portion of the low pressure vapor refrigerant discharges through the low pressure liquid outlet  50  or through another discharge which will assure the eventual return of the refrigerant to the inlet of system compressor  22 . However, it is to be understood that full compression of the low pressure vapor refrigerant is possible if the expander power output is augmented or otherwise balanced with the compressor power input. 
     FIGS. 4 and 5 illustrate the scroll expresser  26  taken along line  4 — 4  and lines  5 — 5  of FIG. 3, respectively. As the orbiting scroll plates  34  and  40  are connected by the key  68 , the orbiting scroll plates  34  and  40  move in the same direction and at the same speed. As shown, the profiles of the generally spiral wraps  45  and  47  of the compressor scroll plates  38  and  40  are preferably the same as the profiles of the generally spiral wraps  37  and  39  of the expansion scroll plates  32  and  34 . However, the direction of the generally spiral wraps  37  and  39  of the expansion scroll plates  32  and  34  are opposite to the direction of the generally spiral wraps  45  and  47  of the compression scroll plates  38  and  40 . Therefore, as the shaft  36  orbits, the compression chambers  54  compress the refrigerant and the expansion chambers  48  expand the refrigerant. 
     FIG. 6 illustrates the scroll expresser  26  taken along line  6 — 6  of FIG.  3 . An off-center crank piece  56  guides the orbiting motion of the shaft  36 . As the center of mass  57  of the shaft  36  is not centered, a counterweight  58  (shown in FIG. 3) is employed to counteract radial inertia loading. An inner sleeve bearing  60  and an outer sleeve bearing  62  are positioned proximate to the interior and exterior, respectively, of the crank piece  56 . 
     Returning to FIG. 3, high pressure refrigerant from the expansion chambers  48  flows through lubrication channels  72  and  74  to lubricate the sleeve bearings  60  and  62 . As high pressure lubrication is provided to the bearings  60  and  62 , a hydrostatic bearing  60  and  62  design is possible. 
     A spring  64  is positioned around the shaft  36  between the orbiting expander scroll plate  34  and the orbiting compressor scroll plate  40 . The spring  64  reduces both axial clearance and axial loading in the scroll expressor  26 . High pressure gases in the compression chambers  54  tend to push the orbiting compressor scroll plate  40  downwardly and away from the corresponding non-orbiting compressor scroll plate  38 , creating axial loading. The spring  64  counteracts this loading and provides a restoring force on the orbiting compressor scroll plate  40 , preventing leakage of refrigerant from the compression chambers  54 . Additionally, by choosing H C , V C , H E , V E , and the number of generally spiral wraps  37 ,  39 ,  45  and  47  of the scrolls plates  32 ,  34 ,  38 , and  40 , a good axial seal in the compressor chambers  54  can be created, further reducing axial loading. 
     The spring  64  also reduces axial clearance in the scroll expresser  26 . As the scroll expresser  26  operates, the scroll plates  32 ,  34 ,  38  and  40  tend to wear, causing leakage of refrigerant and reducing efficiency. The spring  64  applies force on the orbiting scroll plates  34  and  40 , allowing the orbiting scroll plates  34  and  40  to maintain engagement with non-orbiting scroll plates  32  and  38 , respectively, thus reducing leakage of vapor refrigerant due to wear. As the refrigerant in the expansion chambers  48  is about 80% liquid, the liquid refrigerant in the expansion chambers  48  creates an additional seal to further block leakage of the vapor refrigerant from the expansion chambers  48 . 
     The scroll expressor  26  also preferably includes a pair of high pressure vapor inlets  70 . After compression of the refrigerant in the compression chambers  54 , most of the high pressure refrigerant flows along the expresser line  30  to mix with refrigerant exiting the system compressor  22  at the discharge  31 . A small amount of high pressure vapor refrigerant is diverted to enter the expansion chambers  48  through the high pressure vapor inlets  70 . The high pressure vapor refrigerant is used to adjust the revolutions per minute of the shaft  36 , allowing for different capacities of the scroll expressor  26  to be achieved. A control  71  provides the ability to achieve the capacity control. 
     High pressure vapor refrigerant in the expansion chambers  48  and the compression chambers  54  tend to separate the orbiting scroll plates  34  and  40  from the non-orbiting scroll plates  32  and  38 , respectively. Preferably, either or both of the orbiting expander scroll plate  34  and the orbiting compressor scroll plate  40 , respectively, include a hole  85  and  87 . The holes  85  and  87  allow high pressure vapor refrigerant to escape into sealed back-pressure chambers  81  and  83  provided behind either or both the orbiting expander scroll plate  34  and the orbiting compressor scroll plate  40 , respectively. 
     This provides a restoring force to counteract the separating forces as system operating conditions change. However, it is to be understood that either or both of the non-orbiting expander and compressor scroll plates  32  and  38 , respectively, can be adapted to move axially and be provided with back-pressure chambers. 
     FIGS. 7 and 8 illustrate an alternative scroll expresser  126 . The scroll expressor  126  includes a non-orbiting expander scroll plate  132  supported by a base plate  172 , a combined orbiting expander and compressor scroll plate  134 , and a non-orbiting compressor scroll plate  138 . The non-orbiting expander scroll plate  132  and the non-orbiting compressor scroll plate  138  each include a base  133  and  141 , respectively, and a generally spiral wrap,  137  and  145 , respectively. The combined orbiting expander and compressor scroll plate  134  includes a base  135 , a generally spiral expander wrap  139  and a generally spiral compressor wrap  147 . High pressure refrigerant is supplied to the expansion chambers  148  formed between the scroll plates  132  and  134  through a high pressure refrigerant inlet  146 . After expansion, the low pressure liquid refrigerant exits the scroll expresser  126  through the low pressure liquid discharge  150 . The low pressure vapor refrigerant is compressed in the compression chambers  154  and discharged through the high pressure vapor discharger  156 . 
     As shown in FIG. 8, the separation elements  152  prevent the low pressure liquid refrigerant from entering into the compression chambers  154 . Returning to FIG. 7, after expansion, the liquid and vapor expanded refrigerant flows into a expander outlet chamber  173  proximate to the separation element  152 . The vapor expanded refrigerant flows along path B from the expander outlet chamber  173  through the separation element  152  and to the compressor inlet chamber  175  to the compression chambers  154 . As the separation element  152  prevents the flow of liquid refrigerant through the separation element  152 , the expanded liquid refrigerant exits the scroll expressor  126  through the low pressure liquid outlet  150 . The separation element  152  is located between an expressor body  142  and a wall  177 . A clearance  179  exists between the wall  177  and the orbiting scroll plate  134  to allow for orbiting of the orbiting scroll plate  134 . The separation element  152  prevents the passage of liquid refrigerant from the expander outlet chamber  173  to the compressor inlet chamber  175 . 
     The scroll expresser  126  includes three drive mechanisms  180  including a combined crank piece and counterweight  156  which guides the shaft  136  to follow the motion of the orbiting scroll plate  134 . An inner sleeve bearing  162  and an outer sleeve bearing  160  are positioned on the inner surface and outer surface, respectively, of the crank piece  156 . Liquid refrigerant travels through a lubrication channel  174  in the orbiting scroll plates  134  and several lubrication channels  178  in the drive mechanism  180  to lubricate the bearings  160  and  162  to the drive mechanism  180 . The drive mechanism  180  further includes a plug  176  employed to prevent leakage of the lubrication out of the lubrication channel  174 . 
     To counteract the tendency of the plates  132 ,  134  and  138  to separate due to high pressure gases in the chambers  148  and  154 , one of the non-orbiting scroll plates  132  and  138  is adapted to move axially. Only one of the fixed scroll plates  132  and  138  needs to be adapted as the same operating advantages can be realized as if both fixed scroll plates  132  and  138  were adapted. Either of the non-orbiting scroll plates  132  and  138 , respectively, includes a hole  185  and  187 . The holes  185  and  187  allow high pressure vapor refrigerant to escape into sealed back-pressure chambers  181  and  183 , shown schematically, provided behind either the orbiting expander scroll plate  134  and the orbiting compressor scroll plate  140 , respectively. The non-orbiting scroll plates  132  and  138  axially move along dowel pin  144 . 
     There are several benefits to employing the scroll expressor  26 ,  126  of the present invention in a refrigeration system  20 . For one, the efficiency of the refrigerant system  20  can be increased. Additionally, the scroll expresser  26  is compact and less expensive than separate compressor and expansion devices of the prior art. Additionally, using the expander power to directly compress some of the expanded vapor and return it to the system avoids the added mechanical complexity needed to transfer power from the expander to the system compressor as is done in expansion devices of the prior art. 
     The foregoing description is only exemplary of the principles of the invention. Many modifications and variations of the present invention are possible in light of the above teachings. The preferred embodiments of this invention have been disclosed, however, so that one of ordinary skill in the art would recognize that certain modifications would come within the scope of this invention. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specially described. For that reason the following claims should be studied to determine the true scope and content of this invention.