Patent Publication Number: US-9404499-B2

Title: Dual chamber discharge muffler

Description:
FIELD 
     This application claims the benefit of U.S. Provisional Application No. 60/872,589, filed on Dec. 1, 2006. The present disclosure relates to compressors and, more particularly, to compressors with an externally mounted discharge muffler. 
    
    
     BACKGROUND 
     The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
     A class of machines exist in the art generally known as “scroll machines” for the displacement of various types of fluids. Such apparatus may be configured as an expander, a displacement engine, a pump, a compressor, etc., and many features of the present teachings are applicable to any one of these machines. For purposes of illustration, however, the disclosed machines are in the form of a hermetic refrigerant compressor. Generally, a scroll machine comprises two spiral scroll wraps of similar configuration, each mounted on a separate end plate to define a scroll member. 
     The two scroll members are typically inter-fitted together with one of the scroll wraps being rotationally displaced 180° from the other. The machine operates by orbiting one scroll member (the “orbiting scroll”) with respect to the other scroll member (the “fixed scroll” or “non-orbiting scroll”) to make moving line contacts between the flanks of the respective spirals, defining isolated, crescent-shaped pockets of fluid moving from an inlet to an outlet. 
     The spirals are commonly formed as involutes of a circle, and ideally there is no relative rotation between the scroll members during operation; i.e., the motion is purely curvilinear translation (i.e., no rotation of any line in the body). The fluid pockets carry the fluid to be handled from a first zone in the scroll apparatus where a fluid inlet is provided, to a second zone in the apparatus where a fluid outlet is provided. The volume of a sealed pocket changes as it moves from the first zone to the second zone. At any one instant in time, there will be at least one pair of sealed pockets; and when there are several pairs of seal pockets at once, each pair will have different volumes. In a compressor, the second zone (or outlet) is at higher pressure than the first zone (or inlet) and is physically located centrally in the apparatus, the first zone being located at the outer periphery of the apparatus. 
     Two types of contacts define the fluid pockets defined between the scroll members: axially extending tangential line contacts between the spiral faces or flanks of the wraps caused by radial forces (“flank sealing”), and area contacts caused by axial forces between the plain edge surfaces (the “tips”) of each ramp and the opposite end plate (“tip sealing”). For higher efficiency, good sealing must be achieved for both types of contacts. 
     The concept of a scroll-type machine has been recognized as having distinct advantages. For example, scroll machines have high isentropic and volumetric efficiency, and, hence, are relatively small and lightweight for a given capacity. They are, typically, quieter and vibration-less than many compressors types because they do not use large reciprocating parts (e.g., pistons, connecting rods, etc.), and because all fluid flow is in one direction with simultaneous compression in plural opposed pockets, there are less pressure-created vibrations. Such machines also tend to have higher reliability and durability because of the relatively few moving parts utilized, the relatively low velocity of movement between the scrolls, and an inherent forgiveness to fluid contamination. 
     Scroll compressors should not be rotated in reverse, however, as the scrolls can become damaged. One way a scroll compressor may operate in reverse is when compressed refrigerant remaining in the discharge line returns to the compressor and cause the scrolls to run in reverse. This reverse rotation of the scrolls may damage compressor components, including the scrolls, as high-pressure fluid flows to the lower-pressure inlet side of the scrolls. Accordingly, a short discharge line minimizes the volume of refrigerant contained therein and, once the compressor has shut down, a minimal amount of gas will return to the compressor and cause the scrolls to run in reverse. 
     With an externally mounted muffler, a short discharge line is prone to break because the muffler&#39;s larger mass vibrates while the compressor is running. To correct this, the discharge tube for an externally mounted muffler may have generally a longer length of tubing to the compressor. The longer discharge tubing, however, increases the volume of refrigerant present in the discharge line and cause the scrolls to reverse orbit upon shut down. 
     SUMMARY 
     The present teachings provide a dual chamber discharge muffler for a compressor. The dual chambers of the discharge muffler are separated by a check valve that closes upon shutdown of the compressor, which in turn limits the amount of exhaust gases in the discharge muffler that are able to return to the compressor. The dual chambers are formed by dividing the muffler housing with a dividing plate. The dividing plate may receive a fastener that through mounts the muffler to the compressor. 
     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 present disclosure. 
    
    
     
       DRAWINGS 
       The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
         FIG. 1  is a cross-sectional view of a scroll compressor including a dual chamber discharge muffler according to the present teachings; 
         FIG. 2  is a cross-sectional view of a discharge muffler according to the present teachings; 
         FIG. 3  is a close-up cross-sectional view of an oil discharge passage in accordance with the present teachings; 
         FIG. 4  is a cross-sectional view depicting a method of attaching the dual chamber discharge muffler to a compressor; 
         FIGS. 5A and 5B  are cross-sectional views depicting another method of attaching the dual chamber discharge muffler to the compressor; and 
         FIG. 6  is a cross-sectional view of another dual chamber discharge muffler 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. 
     With particular reference to  FIG. 1 , the compressor  2  is shown to include a generally cylindrical hermetic shell  3  having a welded cap  4  at a top portion and a base  5  having a plurality of feet  6  welded at a bottom portion. The cap  4  and the base  5  are fitted to the shell  3  such that an interior volume  7  of the compressor  2  is defined. The cap  4  is provided with a discharge fitting  8  and an inlet fitting (not shown), disposed generally between the cap  4  and base  5 . A discharge muffler system  10  according to the present teachings is in fluid communication with discharge fitting  8 . 
     A drive shaft or crankshaft  11  having an eccentric crank pin  85  at the upper end thereof is rotatably journaled in a bearing  70  in the main bearing housing  27 . A second bearing  71  is disposed in the lower bearing housing  72 . The crankshaft  11  has a relatively large diameter concentric bore  73  at the lower end which communicates with a radially outwardly inclined small diameter bore  74  extending upwardly therefrom to the top of the crankshaft  11 . A stirrer  75  is disposed within the bore  73 . The lower portion of the interior shell  7  defines an oil sump  76  filled with lubricating oil to a level slightly below the lower end of a rotor  19 , and the bore  73  acts as a pump to pump lubricating fluid up the crankshaft  11  and into the passageway  74  and ultimately to all of the various portions of the compressor which require lubrication. 
     The crankshaft  11  is rotatively driven by an electric motor including a stator  15  and windings  17  passing therethrough. The rotor  19  is press fitted on the crankshaft  11  and has upper and lower counterweights  77  and  78 , respectively. 
     The upper surface of the main bearing housing  27  is provided with a flat thrust bearing surface  80  on which an orbiting scroll member  21  is disposed having the usual spiral vane or wrap  23  on the upper surface thereof. A cylindrical hub  25  downwardly projects from the lower surface of orbiting scroll member  21  which has a journal bearing  81  and a drive bushing  82 . 
     Crank pin  85  has a flat on one surface which drivingly engages a flat surface formed in a portion of the drive bushing  82  to provide a radially compliant driving arrangement. An Oldham coupling  25  is provided positioned between the orbiting scroll member  21  and the bearing housing  27  and is keyed to the orbiting scroll member  21  and a non-orbiting scroll member  29  to prevent rotational movement of the orbiting scroll member  21 . 
     Non-orbiting scroll member  29  also includes a wrap  31  positioned in meshing engagement with the wrap  23  of the orbiting scroll member  21 . Non-orbiting scroll member  29  has a centrally disposed discharge passage  33 , which communicates with an upwardly open recess  35  formed in outer surface of cap  4 . Recess  35  is in fluid communication with the discharge fitting  8  such that compressed fluid exits the compressor  2 . Non-orbiting scroll member  29  is designed to be fixedly mounted to bearing housing  29  by a fastener  37 . 
     A dual chamber discharge muffler  10  according to the present teachings will now be described. The muffler  10  is attached to the shell  3  of the compressor  2  and, with particular reference to  FIG. 2 , includes a pair of chambers  12  and  14  separated by a dividing plate  16 . To provide fluid communication between each of the chambers  12  and  14 , the dividing plate  16  supports a check valve assembly  18 . 
     The muffler  10  includes a generally cylindrical muffler housing  20 , and a pair of end caps  22  and  24  connected to the housing  20  by welding or brazing. An upper cap  22  contains an inlet portion  26  of the muffler  10 . The lower cap  24  contains an outlet portion  28  of the muffler  10 . Materials for the housing  20 , upper cap  22 , and lower cap  24  include steel and aluminum. Notwithstanding, these components may be formed of any material known in the art that is of suitable strength and weight. 
     The dividing plate  16 , as stated above, is a substantially planar plate that separates the muffler housing  20  into a pair of chambers  12  and  14 . A first chamber  12 , or inlet chamber  12 , is disposed adjacent the inlet  26  of the muffler  10 . A second chamber  14 , or outlet chamber  14 , is disposed adjacent the outlet  28  of the muffler  10 . Fluidly connecting the inlet and outlet chambers  12  and  14  is the check valve assembly  18 . 
     Although the inlet and outlet chambers  12  and  14  are shown to be relatively equal in size in  FIG. 2 , the present teachings should not be limited to such a configuration. Alternatively, the size of the inlet and outlet chambers  12  and  14  may be unequal. It should be understood, however, that an important aspect of the present teachings is to provide a discharge muffler  10  that has a large enough volume to sufficiently reduce the discharge pulses emitted by the compressor  2 . In this regard, the collective volume of the inlet and outlet chamber  12  and  14  must be large enough to effectively reduce the discharge pulses emitted by the compressor  2 . 
     Check valve assembly  18  includes a check valve  86  which is a flat disc with a center opening  87 . This opening  87  along with a pair of fluid pathways  32  in check valve seat  30  allow exhaust gases emitted by the compressor  2  to pass through muffler  10  as shown by the arrows in  FIG. 2 . When the compressor  2  is running, the compressor  2  emits exhaust gases that leave the compressor  2  through a discharge line  39  that enter the discharge muffler  10  through the inlet  26 . Upon entry of the exhaust gases in the discharge muffler  10 , a sufficient pressure gradient is formed in the muffler  10  to move check valve  86  off sealing surface  88  of valve seat  30  and to allow flow through pathways  32  in valve seat  30  and opening  87  in check valve  86 . When the compressor  2  is not running or shuts down, the pressure gradient reduces sufficiently such that check valve  86  moves into contact with surface  88  of valve seat  30  closing opening  87  in check valve  30  and pathways  32  in valve seat  30  subsequently shutting off fluid communication between the inlet chamber  12  and the outlet chamber  14 . 
     The check valve  86  preferably is disposed between a pair of fluid conduits  34  and  36  that are supported by the dividing plate  16 . A first conduit  34 , or extension  34 , extends upward from the dividing plate  16  into the inlet chamber  12 . A second conduit  36 , or extension  36 , extends downward from the dividing plate  16  into the outlet chamber  14 . The first conduit  34  is provided with a portion  38  that is supported by the dividing plate  16 . To connect the first conduit  34  to the dividing plate  16 , the first conduit  34  is preferably attached by welding or brazing. The portion  38  connecting the first conduit  34  to the dividing plate  16  is configured to act as a fitting that is adapted to receive a fitting portion  40  of the second conduit  36 . In this manner, the first and second conduits  34  and  36  can be securely fastened to each other by welding or brazing. Alternatively, the fitting  38  of the first conduit  34  can include a threading (not shown) that corresponds to a threading (not shown) formed on the fitting portion  40  of the second conduit  36 . 
     Referring to  FIG. 3 , a unique feature of the first conduit  34  is that it is provided with an oil passage  42 . As best shown in  FIG. 3 , the oil passage  42  is formed in the fitting portion  38  or base  38  of the first conduit  34 . Due to the expansion of the exhaust gas when it enters the muffler  10 , the velocity of the exhaust gas will reduce. This reduction in gas velocity will allow some of the entrained oil in the gas to condense and drop out of the exhaust gas. Because of the length of the first conduit  34 , the amount of oil  44  that may collect can be quite large. 
     Notwithstanding, the oil passage  42  allows any oil  44  that may collect in the inlet chamber  12  to drain slowly through the check valve  86 . By controlling the drainage of the oil  44 , the oil  44  is prevented from building up inside the check valve  86 . The oil passage  42  allows the oil  44  to drain by gravity flow or by a pressure drop that will be caused by the exhaust gas flowing through the inlet chamber  12  across the pool of oil  44  at the bottom of the inlet chamber  12 . 
     The effectiveness of the muffler  10  in reducing pressure pulsations in the compressor discharge gas flow is determined by the relative sizes of the inlet portion  26 , muffler housing  20 , inlet chamber  12 , outlet chamber  14 , and conduits  34  and  36 . It is a preferred configuration of this design that partition  16  be located approximately half-way between inlet portion  24  and outlet portion  26 . Further, it is preferred that the combined length of conduits  34  and  36  be approximately equal to one-half the distance between inlet portion  24  and outlet portion  26 . It should also be understood that the individual lengths and diameters of the conduits  34  and  36  may be adjusted (i.e., lengthened or widened, respectively). In other words, the lengths and diameters of the conduits  34  and  36  may be approximately the same or different. 
     Referring to  FIG. 4 , to connect the discharge muffler  10  to the compressor  2 , the discharge muffler  10  is provided with an internal sleeve or spacer  46 . The spacer  46  is, by way of non-limiting example, a generally cylindrical shaped sleeve that passes through a central portion  48  of the muffler housing  20 . That is, the spacer  46  is diametrically disposed through the muffler housing  20 . To connect the spacer  46  to the muffler housing  20 , the spacer  46  may be brazed or welded to the muffler housing  20 . 
     The spacer  46  provides a pathway for a fastener  50  such as a bolt or screw that fixes the discharge muffler  10  to the compressor shell  3 . To fix the discharge muffler  10  to the compressor shell  3 , the fastener  50  is coupled to a spud  54  which is fixedly attached to the compressor shell  3 . The spud  54  may be attached to the compressor shell  3  by welding or brazing, or in any method known to one skilled in the art. 
     Although the spacer  46  is described and shown as being diametrically disposed through the central portion  48  of the muffler housing  20 , the present teachings should not be limited thereto. That is, the spacer  46  assists in rigidly securing the muffler  10  to the shell  3  of the compressor  2  by controlling a center of mass of the muffler  10 . By controlling the center of mass of the muffler  10 , vibration of the muffler  10  during operation of the compressor  2  can be eliminated, or at least substantially minimized. Accordingly, the spacer  46  may used to connect the muffler  10  to the shell  3  of the compressor  2  in any manner that is sufficient in controlling a center of mass of the muffler  10 . That is, it is contemplated that the spacer  46  may be attached to an outer surface of the muffler housing  20  without departing from the spirit and scope of the present teachings. 
     As stated above, the discharge muffler  10  is rigidly mounted to the compressor shell  3  in a manner such that vibrations are eliminated, or at least substantially minimized. Moreover, by mounting the discharge muffler  10  to the compressor shell  3  in this manner, the discharge line  39  needed to supply the exhaust gases from the compressor  2  into the discharge muffler  10  is kept at a minimal length. Accordingly, any exhaust gas present in the discharge line  39 , and in turn the discharge muffler  10 , is kept to a minimum such that upon shutdown of the compressor  2  the discharge gas will not return through the discharge line  39  to the compressor  2  and run the scrolls  21  and  29  in reverse. Damage to the sensitive scroll components of the compressor  2 , therefore, can be avoided. 
     The dual chambers  12  and  14  separated by the check valve  86  also assist in this manner. That is, as stated above, when the compressor  2  is not operating or shuts down, the pressure gradient present in the discharge muffler  10  will reduce sufficiently to allow the fluid pathways  87  of the check valve  86  to close. As such, the amount of exhaust gases that are able to flow back into the compressor  2  and cause reverse rotation of the scrolls  21  and  29  is further reduced. This is because the only exhaust gas that may flow back into the compressor  2  will be the exhaust gases in the discharge line  39  that leads to the muffler  10 , as well as the exhaust gases present in the inlet chamber  12  of the muffler  10 . 
     Accordingly, as stated above with reference to  FIG. 2 , the inlet chamber  12  and outlet chamber  14  may have differing volumes. In this regard, it may be preferable to have an inlet chamber  12  with a volume that is sufficiently less than the volume of the outlet chamber  14  to reduce the amount of exhaust gases that are able to return to the compressor  2  on shutdown. Alternatively, the volume of the inlet chamber  12  may be greater than the volume of the outlet chamber  14 . Regardless, it should be understood that the volume of the inlet chamber  12  should be a sufficient size to both reduce the discharge pulses emitted by the compressor  2  and reduce the amount of exhaust gas that may return to the compressor  2  on shutdown. 
     Now referring to  FIGS. 5A and 5B , the dividing plate  16  has been adapted to act as the spacer  46  for receiving the fastener  50  that secures the discharge muffler  10  to the compressor shell  3 . The dividing plate  16  is provided with a cylindrical through hole  56  that passes diametrically though the muffler housing  20 . The through hole  56  is adapted to act as the spacer  46  that receives the fastener  50  that rigidly secures the muffler  10  to the compressor shell  3 . By configuring the dividing plate  16  to additionally act as the spacer  46 , the number of components that compose the muffler  10  can be reduced to reduce manufacturing costs, as well as reduce manufacturing time. 
     To provide room for the through hole  56  adapted to act as a spacer  46 , the dividing plate  16  is configured to support an extension portion  58  of the first conduit  34 . In this manner, the fitting portions  38  and  40  that connect the first conduit  34  and second conduit  36  are disposed in the outlet chamber  14  of the discharge muffler  10 . Further, the check valve  86  that is supported between the fitting portions  38  and  40  of the first and second conduits  34  and  36  is also disposed in the outlet chamber  14 . Regardless, it should be understood that the fitting portions  38  and  40  may also be disposed in the inlet chamber  12  without departing from the spirit and scope of the present teachings. Further, the oil discharge outlet  42  is formed in the extension portion  58  of the first conduit  34 . Accordingly, oil  44  and fluid is able to drain from the inlet chamber  12  to the outlet chamber  14  through the check valve  86  as well. 
     Although the present teachings have been described relative to an externally mounted discharge muffler  10 , the present teachings should not be limited thereto. In contrast, the present teachings are also adaptable to a discharge muffler  10  that is integral with the compressor  2 . As shown in  FIG. 6 , the dual chamber discharge muffler  10  has been adapted to fit on top of the compressor  60 . The inlet chamber  12  of the discharge muffler  10  is directly adjacent the outlet  62  from the compressor  60  and is fluidly connected to the outlet chamber  14  of the muffler by a tube or hose  64 . 
     As exhaust gases exit the compressor  60 , the gases will travel through the first chamber  12  and enter the tube  64  as shown by the arrows in  FIG. 6 . Present within the tube  64  is a check valve  30  that operates like the check valves described above relative to the other configurations. More particularly, as exhaust gases enter the inlet chamber  12  of the muffler  10 , the pressure gradient in the chamber  12  will rise to a point that the fluid pathways of the check valve  30  will open to allow fluid communication between the inlet chamber  12  and the outlet chamber  14 . The gases will then enter the outlet chamber  14  and exit the muffler  10  through an exhaust fitting  66 . The tube  64  that houses the check valve  30  may be a flexible tube made of an elastomeric, rubber, or polymeric material. Notwithstanding, the tube  64  may also be formed of a metal material such as copper or aluminum. 
     When the compressor  60  has shut down, the pressure gradient in the inlet chamber  12  will lower to a point such that the fluid pathways of the check valve  30  will close to shut down fluid communication between the inlet chamber  12  and the outlet chamber  14 . Accordingly, only gases present in the tube  64  and inlet chamber  12  will be able to reenter the compressor  60 . In this manner, the reverse rotation of the scrolls  21  and  29  will be effectively and substantially minimized. 
     It should be understood that although the present teachings have been described relative to use with a scroll compressor, the present teachings should not be limited thereto. In contrast, the discharge mufflers of the present teachings are adaptable to any type of compressor known in the art including rotary, reciprocating, and orbiting types because the mufflers of the present teachings are proficient in reducing discharge pulses emitted by a compressor, reducing a temperature of the exhaust gases, and preventing the build up of back pressure in the compressor.