Abstract:
A compressor for an air conditioning system comprises a piston and a pin. The piston comprises an aperture forming a piston bearing surface and a lubrication port in communication with the aperture. The pin comprises a pin bearing surface and the pin is received within the aperture to form an interface between the pin bearing surface and the piston bearing surface. In another embodiment, a method of lubricating within a compressor comprises rotating a crankshaft within a crankcase, introducing lubricant into the crankcase; and contacting the lubricant with a portion of a pin disposed within a piston via a lubrication port in the piston. In yet another embodiment, a piston for a compressor comprises an aperture forming a piston bearing surface and a lubrication port in communication with the aperture.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    Not Applicable. 
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not Applicable. 
       BACKGROUND 
       [0003]    Some conventional refrigeration and/or air conditioning compressors comprise a motor, a crankshaft rotated by the motor, and a reciprocating piston driven by the crankshaft. The reciprocating piston is typically connected to the crankshaft via a connecting arm, which is sometimes also referred to as a “connecting rod” or “con rod.” The connection is made by extending the crankshaft through an aperture in a first end of the connecting arm and extending a pin through apertures in a second end of the connecting arm and the piston, respectively. In operation, the connecting arm moves with respect to both the crankshaft and the pin, and vice versa. Therefore, frictional interfaces are formed where surfaces of the connecting arm engage surfaces of each of the pin and the crankshaft, and these frictional interfaces are typically lubricated. 
         [0004]    In some compressors, such as hermetically sealed compressors that conventionally use mineral oil lubricant, for example, splash lubrication is employed whereby the movement of at least the crankshaft and the connecting arm interact with a supply of lubricant, thereby causing the lubricant to splash onto components needing lubrication and sometimes forms a fog or mist within the compressor that also aids in lubricating components. It is not uncommon for there to be some mixing of the lubricants and the refrigerants, such as R-22, within the compressor. 
       SUMMARY OF THE DISCLOSURE 
       [0005]    A compressor for an air conditioning system is disclosed. In some embodiments, the compressor comprises a piston and a pin. The piston comprises an aperture forming a piston bearing surface and a lubrication port in communication with the aperture. The pin comprises a pin bearing surface and the pin is received within the aperture to form an interface between the pin bearing surface and the piston bearing surface. 
         [0006]    In another aspect, the present disclosure relates to methods for lubricating within a compressor, comprising rotating a crankshaft within a crankcase, introducing lubricant into the crankcase, and contacting the lubricant with a portion of a pin disposed within a piston via a lubrication port in the piston. 
         [0007]    Further, a piston for a compressor is disclosed. In some embodiments, the piston comprises an aperture forming a piston bearing surface and a lubrication port in communication with the aperture. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    For a more detailed description of the various embodiments of the compressor with improved lubrication, reference will now be made to the accompanying drawings, wherein: 
           [0009]      FIG. 1  is an oblique cut-away view of an embodiment of a compressor employing improved lubrication features and methods; 
           [0010]      FIG. 2  is an oblique view of some of the moving parts of the compressor of  FIG. 1 ; 
           [0011]      FIG. 3  is a top orthogonal view of a connecting arm of the compressor of  FIG. 1 ; 
           [0012]      FIG. 4  is a side orthogonal partial cross-sectional view of a pin of the compressor of  FIG. 1 ; 
           [0013]      FIG. 5  is a side orthogonal view of a piston of the compressor of  FIG. 1 ; 
           [0014]      FIG. 6  is an oblique view of the piston of  FIG. 5 ; and 
           [0015]      FIG. 7  is a bottom orthogonal view of the piston of  FIG. 5 . 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    Some refrigerants used in compressors are not amenable to being mixed with mineral oil, so alternative lubricants are used in such compressors. For example, in compressors using the refrigerant R-410A, lubricants such as polyol ester, polyvinylchloride or polyol ester/akylbenzine blends are used instead of mineral oil. These alternative lubricants tend not to splash and/or form a fog or mist as well as mineral oil, and therefore, may not sufficiently lubricate frictional interfaces between moving components. Specifically, the bearing surfaces between the pin and the piston may not be well lubricated through splash lubrication of the polyol ester, polyvinylchloride or polyol ester/akylbenzine blends used with the refrigerant R-410A and/or other refrigerants. 
         [0017]    Referring now to  FIGS. 1 and 2  in the drawings, an embodiment of a compressor  100  employing improved lubrication features and methods is shown, with  FIG. 1  illustrating the compressor  100  more completely and  FIG. 2  illustrating only certain moving parts of the compressor  100 . The compressor  100  generally comprises an outer housing  102 , that may be hermetically sealed, for housing an electrical motor  104 , a deviated crankshaft  106 , a connecting arm  108 , a pin  110  (not visible in  FIG. 1 ), and a piston  112 . 
         [0018]    An upper shank  114  of the crankshaft  106  is received within an armature  116  of the motor  104  near an upper end  118  of the compressor  100 , while a lower shank  120  of the crankshaft  106  is received within a lower bearing  122  near a lower end  124  of the compressor  100 . The upper shank  114  and lower shank  120  lie coaxially along an axis of rotation  126  about which the motor  104  rotates the crankshaft  106 . The upper shank  114  is also received within an upper bearing  123  that serves to retain the upper shank  114  concentric with the axis of rotation  126  while allowing rotation of the upper shank  114  about the axis of rotation  126 . A transition shank  128  is joined between the upper shank  114  and the lower shank  120  and is offset from and generally parallel to the axis of rotation  126 . 
         [0019]    The connecting arm  108  comprises a shaft ring  130  forming an aperture for receiving and encircling an eccentric bearing surface  129  of the transition shank  128  and a pin ring  132  forming an aperture for receiving and encircling the pin  110  (discussed infra). The eccentric bearing surface  129  is formed substantially as a smooth cylindrical surface with its lengthwise axis oriented generally parallel to the axis of rotation  126 . The piston  112  is generally received within a cylindrical bore  133  of the compressor  100  and connected to the pin ring  132  of the connecting arm  108  via the pin  110 . The open space within the compressor  100  that generally houses the transition shank  128  and the shaft ring  130 , and which extends generally from a top surface of the lower bearing  122  to a top of the upper bearing  123 , is referred to as the crankcase  134 . During operation, discussed infra, a centrifugal pump (not shown) forces lubricant into the crankcase  134  through a lower lubricant delivery aperture  135  formed longitudinally through the lower shank  120 . 
         [0020]    Referring now to  FIG. 3 , a top orthogonal view of the connecting arm  108  is shown to depict its features in greater detail. The connecting arm  108  further comprises a bridge  136  joining the shaft ring  130  and the pin ring  132 . The connecting arm  108  is well suited for alternatingly withstanding high tensile and compressive forces along a path between the shaft ring  130  and the pin ring  132 . The shaft ring  130  of the connecting arm  108  comprises an aperture  131  forming a shaft ring bearing surface  138  that is generally smooth for interfacing with the complementary smooth eccentric bearing surface  129  of the crankshaft  106 . The shaft ring bearing surface  138  has a smoothness rating sufficient to facilitate movement and minimize friction when the eccentric bearing surface  129  is received within the shaft ring  130  and relative rotation occurs between the eccentric bearing surface  129  and the shaft ring bearing surface  138 . In an embodiment, the smoothness rating of the shaft ring bearing surface  138  is 15 microinches Ra. Of course, in alternative embodiments, one or both of the shaft ring  130  and the transition shank  128  may have different smoothness ratings or be outfitted with bearing components, friction reducing coatings or other systems or devices for facilitating relative movement therebetween. 
         [0021]    The pin ring  132  of the connecting arm  108  comprises an aperture  137  forming a pin ring bearing surface  140  that is generally smooth for interfacing with a complementary smooth surface of the pin  110 . The pin ring bearing surface  140  has a smoothness rating sufficient to facilitate movement and minimize friction when the pin  110  is received within the pin ring  132  and relative rotation occurs. In an embodiment, the smoothness rating of the pin ring bearing surface  140  is 15 microinches Ra. Of course, in alternative embodiments, one or both of the pin ring  132  and the pin  110  may have different smoothness ratings or may be outfitted with bearing components, friction reducing coatings, or other systems or devices for enabling relative movement therebetween. 
         [0022]    Referring now to  FIG. 4 , a side orthogonal view of the pin  110  is shown to depict its features in greater detail. The pin  110  is generally cylindrical in shape and comprises a pin bearing surface  142  that is generally smooth for interfacing with complementary smooth bearing surfaces of the connecting arm  108  and the piston  112 . In an embodiment, the pin bearing surface  142  has a smoothness rating of 2 microinches Ra. Of course, in alternative embodiments, the pin bearing surface  142  may have a different smoothness rating. Cavities  143  (only one shown) are located at each end of the generally cylindrical pin  110  and serve to accept endcaps  145 . The end caps  145  are inserted into cavities  143 , and a portion of each endcap  145  protrudes beyond any portion of the pin bearing surface  142 . At least the outermost portions of the endcaps  145  are constructed to have a somewhat smooth surface for providing low friction interfacing with the cylindrical bore  133  of the compressor  100 . In an embodiment, the endcaps  145  are constructed of nylon, but in alternative embodiments, the endcaps may be constructed of any other suitable material for preventing binding with the bore  133 . In the embodiment shown, the piston  112  is a unitary aluminum die-cast component. However, in alternative embodiments, a piston may be formed by joining two or more piston components, which are substantially similar to the outer wall  144 , the pressure cap  150 , and the bosses  156 , to form the piston. Also, a piston may alternatively be formed using any other suitable manufacturing process or combination of manufacturing processes and the piston may be constructed from a different material or combination of materials. 
         [0023]    Referring now to  FIGS. 5-7 , various views of the piston  112  are shown to depict its features in greater detail. The piston  112  generally comprises a cylindrical tubular outer wall  144  having an outer surface  146  and an inner surface  148 . One end of the outer wall  144  is sealed by a pressure cap  150  that is generally the leading portion of the piston  112  during a compression stroke of the piston  112  in the bore  133 . In other words, the pressure cap  150  leads movement of the piston  112  when the piston  112  moves away from the crankcase  134  of the compressor  100 . A ring seat  152 , formed as a recessed groove in the outer wall  144 , is located near the junction between the outer wall  144  and the pressure cap  150 . The ring seat  152  is configured to receive a ring seal (not shown) which, when installed onto the piston  112 , is configured to provide a seal between the piston  112  and the cylindrical bore  133  disposed in the compressor, effectively providing a movable pressure partition within the bore  133 . In an embodiment, the ring seal may be constructed of cast iron, but in alternative embodiments, the ring seal could be constructed of any other suitable sealing material, such as an elastomer. In an alternative embodiment, the piston does not comprise a ring seat and associated ring seal for providing the pressure partition with the bore, but instead, the outer wall of the piston directly contacts the wall of the bore. 
         [0024]    The outer wall  144  is also formed with two opposing pin apertures  154  extending radially therethrough and being sized and shaped for receiving the pin  110 . Further, two opposing bosses  156  associated with the pin apertures  154  protrude inward from the inner surface  148  of the outer wall  144  of the piston  112 . The bosses  156  serve to strengthen the piston  112  by bolstering its ability to withstand forces exerted on it by the pin  110  while the pin  110  is inserted through the pin apertures  154  along a pin axis of rotation  158 . The bosses  156  each comprise two strengthening posts  160  that extend generally from the inside of the pressure cap  150  to an inner end  162  of the piston. In alternative embodiments, a piston may not comprise strengthening posts such as strengthening posts  160 . The inner end  162  of the piston  112  is generally the trailing portion of the piston  112  during a compression stroke of the piston  112  in the bore  133 . In other words, the inner end  162  trails movement of the piston  112  when the piston  112  moves away from the crankcase  134  of the compressor  100 . Between each set of adjacent posts  160 , and generally extending inward from the inner surface  148  toward a center of the piston  112 , each boss  156  further comprises an annular wall  164  that joins with the respective pin apertures  154  to form piston bearing surfaces  166  that extend along the pin axis of rotation  158 . The piston bearing surfaces  166  are generally smooth for interfacing with the smooth pin bearing surface  142  of the pin  110 . In an embodiment, the piston bearing surfaces  166  have a smoothness rating of 17 microinches Ra. Of course, in alternative embodiments, the piston bearing surfaces  166  may have a different smoothness rating. 
         [0025]    Lubrication ports  168  extend axially through each annular wall  164  of the bosses  156  and communicate with the pin apertures  154  extending radially through the piston outer wall  144 . In various embodiments, the lubrication ports  168  may be formed as cylindrical apertures or slots that are cast, milled, drilled or machined into the annular walls  164 . As best shown in  FIG. 1 , the lubrication ports  168  are disposed closest to the crankcase  134  when the piston  112  is installed in the cylindrical bore  133  of the compressor  100 . As such, the connection between the lubrication ports  168  and the pin apertures  154  thereby creates a fluid path from the crankcase  134  to the interior of the bosses  156 . Thus, lubricant can contact both the pin bearing surfaces  142  that extend through the bosses  156  as well the piston bearing surfaces  166  of the bosses  156 . In alternative embodiments, the lubrication ports may be formed in any size and/or shape, and in any fashion that creates fluid paths between the crankcase and the pin and piston bearing surfaces sufficient to permit adequate lubrication of these surfaces using mineral oil or other lubricants. 
         [0026]    Referring again to  FIGS. 1 and 2 , the connections between the connecting arm  108 , the pin  110  and the piston  112  are explained in more detail. When fully assembled, the components of the compressor  100  are arranged so that the pin  110  acts as a dual bearing or redundant bearing. As most clearly shown in  FIG. 2 , the arm  108 , the pin  110  and the piston  112  are assembled by first placing the pin ring  132  of the arm  108  in a position substantially within the piston  112 , between the bosses  156 , and coaxially aligned with the pin axis of rotation  158 . In this embodiment, two thin and substantially flat shims  170  are shown located coaxial to the pin axis of rotation  158 , with one shim  170  between each side of the pin ring  132  and the adjacent bosses  156 . The shims  170  serve to reduce wear of the bosses  156  and the pin ring  132  as the pin ring  132  moves relative to the bosses  156 . However, in alternative embodiments, shims may be omitted or replaced by other suitable devices for reducing wear of the components. Once the shims  170  and the pin ring  132  are substantially located within the piston  112  and coaxial with the pin axis of rotation  158 , an end of the pin  110  is inserted through a pin aperture  154  in the nearest adjacent boss  156 , through the nearest adjacent shim  170 , through the pin ring  132 , through the remaining shim  170  and through the remaining boss  156 . The pin  110  is ultimately positioned so that the outermost extending portions of the endcaps  145  extend substantially to the outer surface  146  of the piston  112  at both ends of the pin  110 . This arrangement provides a dual bearing or redundant bearing feature in that the pin  110  is free to rotate about the pin axis of rotation  158  relative to each of the piston  112  and the pin ring  132 . In an alternative embodiment of a compressor, the pin may not serve as a redundant bearing as described above, but rather, the pin may only serve to rotate relative to the piston. More specifically, in that alternative embodiment, the pin may be substantially rigidly fixed to the rod by press fitting the pin into the pin ring, by application of thermal heat shrink to secure the pin relative to the rod, through the use of a mechanical fastening device, or any other suitable device or system for reducing relative rotation of the pin relative to the rod, namely, the relative rotation between the pin bearing surface and the pin ring bearing surface. 
         [0027]    Referring again to  FIG. 1 , the operation of the compressor is now explained. Generally, lubricant (not shown) pools near the lower bearing  122  and remains accumulated to a level substantially near the interface of the lower shank  120  and the transition shank  128 . Compressor  100  functionality begins when the motor  104  is energized resulting in the armature  116  exerting a rotational force on the crankshaft  106 . Since the armature  116  and the lower bearing  122  allow rotation of the crankshaft  106  about the axis of rotation  126 , the upper shank  114  and lower shank  120  rotate about the axis of rotation  126  while the transition shank  128  rotates in a circular orbit about the axis of rotation  126 . Since the connecting arm  108  is connected to the transition shank  128  via the shaft ring  130 , the arm  108  is carried by the transition shank  128  in the same orbital path, and the transition shank  128  simultaneously rotates within the shaft ring  130 . Since the shaft ring  130  is rigidly attached to the pin ring  132  via the bridge  136 , and the pin ring  132  is connected to the piston  112  via the pin  110 , the entire arm  108  is reciprocated along the central axis of the cylindrical bore  133  in which the piston  112  is housed. Necessarily, the piston  112  follows the movement of the arm  108  in that the piston  112  is resultantly reciprocated within the bore  133  toward and away from the crankcase  134 . 
         [0028]    During such reciprocation and movement of the above-described components, the pin  110  is free to rotate about the pin axis of rotation  158 , and the rotation may be relative to one or both of the pin ring  132  and the bosses  156 . More specifically, the pin bearing surface  142  of the pin  110  is not only free to rotate relative to the pin ring bearing surface  140  of the pin ring  132 , but also relative to the piston bearing surfaces  166  of the bosses  156 . During rotation of the crankshaft  106 , a centrifugal pump (not shown) pumps lubricant from the above-described pooled lubricant and through the lower lubricant delivery aperture  135  of the lower shank  120  of the crankshaft  106 . In an embodiment, the crankshaft  106  is rotated at approximately 3500 RPM, although in alternative embodiments, the crankshaft may be rotated at higher or lower speeds or may even be operated at varying speeds. As the lubricant exits the lower lubrication delivery aperture  135  near the interface of the lower shank  120  and the transition shank  128 , the rotation of the crankshaft  106  cause the lubricant to be splashed all about within the crankcase  134 . Lubricant is also passed through the crankshaft  106  so that it exits the upper shank  114  through two upper lubrication delivery apertures  139 . The upper lubrication delivery apertures  139  are positioned along the length of the upper shank  114  so that they are aligned with and generally encircled by the upper bearing  123 . When lubricant exits the upper lubrication delivery apertures  139 , the interface between the upper shank  114  and the upper bearing  123  is lubricated. Further, the lubricant subsequently exits the space between the upper shank  114  and the upper bearing  123  at the bottom end of the upper bearing  123  and enters the crankcase  134  to thereafter be splashed all about within the crankcase  134  as described above. A lubricant delivery aperture substantially similar to the upper lubrication delivery aperture  139  is formed in the transition shank  128  and similarly lubricates the interface between the eccentric bearing surface  129  and the shaft ring bearing surface  138 . The lubricant subsequently exits the space between the eccentric bearing surface  129  and the shaft ring bearing surface  138  at both the top and bottom ends of the shaft ring bearing surface  138  and enters the crankcase  134  to thereafter be splashed all about within the crankcase  134  as described above. The splashed lubricant may be struck again by the rotating and translating components of the compressor  100  within the crankcase  134 . This process of splashing and striking the lubricant often forms a mist or fog of lubricant within the crankcase  134  that generally lubricates all surfaces that come in contact with the mist or fog. 
         [0029]    However, in an embodiment, at least some of the splashed and stricken lubricant is directed or deflected to have a trajectory that terminates within or through the lubrication ports  168 . The lubricant that reaches the lubrication ports  168 , or is passed through the lubrication ports  168 , directly aids in lubricating the interface between the pin bearing surface  142  and the piston bearing surface  166 . In an embodiment, some of the lubricant directly strikes the pin bearing surface  142  by passing through the lubrication ports  168 . 
         [0030]    To maximize the amount of pin bearing surface  142  exposed to direct lubrication through the lubrication ports  168 , the size of the lubrication ports  168  may be maximized until enlarging the lubrication ports  168  any more would unduly compromise the strength of the bosses  156 . In particular, the piston  112  must be able to withstand the forces exerted on it by the pin  110  to push it away from and pull it towards the crankcase  134 . In an embodiment, the force exerted on the piston  112  by the pin  110  to pull the piston  112  toward the crankcase  134  is only about 10% of the force exerted on the piston  112  by the pin  110  to push the piston  112  away from the crankcase  134 . Accordingly, those force differentials must be considered when maximizing the size of the lubrication ports. 
         [0031]    As evinced by the discussion above, the compressor  100  employing improved lubrication features and methods, and the alternative embodiments disclosed, provide the ability to adequately lubricate the interface between a pin and a piston when that pin is used to connect an arm to the piston. The improved lubrication of the interface between the pin and the piston results from the lubrication ports associated with the bosses since the lubrication ports offer unimpeded access for the lubricant to reach the pin through the lubrication ports. Further, such adequate lubrication is achieved by the above disclosed compressor embodiments even when the compressors use R-410A refrigerant and lubricants that do not splash as readily as mineral oil. 
         [0032]    While various embodiments of compressors have been shown and described, modifications thereof can be made by one skilled in the art without departing from the spirit or teaching of this disclosure. The embodiments described herein are representative only and are not limiting. Many variations and modifications of the apparatus and methods are possible and are within the scope of the disclosure. Accordingly, the scope of protection is not limited to the embodiments described herein, but is only limited by the claims that follow, the scope of which shall include all equivalents of the subject matter of the claims.