Patent Publication Number: US-2006002801-A1

Title: Rocker compressor mechanism

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a reciprocating piston compressor, and more particularly to a rocker mechanism for converting rotational motion of the rotor of a compressor motor into linear motion for reciprocating one or more pistons in the compression mechanism.  
      2. Description of the Related Art  
      Reciprocating piston compressors or pumps use reciprocation motion of a piston within a cylinder to compress fluids such as refrigerant. The compressors or pumps are typically provided with a source of power and a drive shaft. The source of power may be a drive motor having the drive shaft attached thereto such that the drive motor induces rotation of the shaft. The compression or pumping mechanism is operatively connected to the opposite end of the drive shaft.  
      In one example of a reciprocating piston compressor, a housing including a cylinder block and cylinder head is provided to encase the compression mechanism. The drive shaft is an input shaft which is rotatably mounted in the housing having a portion of the shaft extending outwardly from one end of the housing. The motor is also located outside of the housing and engages the external portion of the drive shaft. A mechanism is provided between the drive shaft and the reciprocating pistons to convert rotational movement of the drive shaft into linear motion of the pistons. The mechanism includes an inclined surface fixedly mounted to one end of the drive shaft for rotation therewith. A wobble plate is non-rotatably mounted on top of the inclined surface via a centrally located ball joint or roller bearing. Pistons are mounted to the wobble plate and are received in cylinders defined in the cylinder block. As the inclined surface rotates the wobble plate rocks about its central point causing the pistons to reciprocate within their cylinders to compress or pump fluid located in the cylinders.  
      A further example of a reciprocating piston compressor includes a housing in which the motor and compression mechanism are mounted. The drive shaft is fixedly mounted in the rotor of the motor for rotation therewith. The motor is mounted on top of a cylinder block having a cylinder head attached thereto. One cylinder is defined in the cylinder block to receive each piston. The drive shaft extends into the cylinder clock and has a cam portion integrally formed with the drive shaft at points along the shaft in alignment with the cylinders. The pistons are mounted on the cam portions and as the drive shaft is rotatably driven by the motor, the pistons reciprocate within the respective cylinders to compress or pump fluid located in the cylinders.  
     SUMMARY OF THE INVENTION  
      The present invention provides a reciprocating piston compressor having a rocker mechanism for converting rotational motion of the rotor of an electric motor into linear motion for reciprocating one or more pistons. The drive shaft of the reciprocating piston compressor is fixedly mounted in the rotor for rotation therewith. A mounting plate having an inclined surface is integrally formed at the upper end of the drive shaft. The inclined surface is operatively coupled to one or more pistons by a bearing having an inner and outer race, a second inclined plate, or a second flat plate.  
      The invention comprises, in one form thereof, a compressor assembly for compressing a vapor. The compressor assembly includes a compression mechanism and a motor operably coupled to the compression mechanism. The compression mechanism includes at least one piston reciprocatingly mounted therein. A drive shaft is mounted in the motor for rotation therewith and a support plate is mounted to the motor with the drive shaft extending through the support plate. A rocker mechanism for converting rotational motion of the drive shaft into reciprocating motion of the piston is also provided. The rocker mechanism includes a mounting plate, having an inclined surface, integrally formed with one end of the drive shaft and means for linking the mounting plate and the piston such that when the drive shaft rotates, the piston reciprocates within the compression mechanism. The means for linking the mounting plate and the piston is operatively coupled to the mounting plate and is mounted directly to the piston.  
      The invention comprises, in another form thereof, a compressor assembly for compressing a vapor that includes a compression mechanism and a motor operably coupled to the compression mechanism. The compression mechanism includes at least one piston reciprocatingly mounted therein. A drive shaft is mounted in the motor for rotation therewith. A support plate is mounted to the motor with the drive shaft extending through the support plate. Also provided is a rocker mechanism for converting rotational motion of the drive shaft into reciprocating motion of the piston. The rocker mechanism includes a mounting plate integrally formed with one end of the drive shaft, the mounting plate having an inclined surface, a bearing fixedly mounted to the mounting plate, and a linkage arm operatively coupling the bearing and the piston.  
      The invention comprises, in a further form thereof, a compressor assembly for compressing a vapor. The compressor assembly includes a compression mechanism and a motor operably coupled to the compression mechanism. The compression mechanism includes at least one piston reciprocatingly mounted therein. A drive shaft is mounted in the motor for rotation therewith and a support plate is mounted to the motor with the drive shaft extending through the support plate. A rocker mechanism for converting rotational motion of the drive shaft into reciprocating motion of the piston is also provided. The rocker mechanism includes a mounting plate integrally formed with one end of the drive shaft, the mounting plate having an inclined surface, and an actuating plate. The actuating plate has an inclined surface in operative contact with the mounting plate inclined surface.  
      The invention comprises, in one form thereof, a compressor assembly for compressing a vapor. The compressor assembly includes a compression mechanism and a motor operably coupled to the compression mechanism. The compression mechanism includes at least one piston reciprocatingly mounted therein. A drive shaft is mounted in the motor for rotation therewith and a support plate mounted to the motor with the drive shaft extending through the support plate. A rocker mechanism for converting rotational motion of the drive shaft into reciprocating motion of the piston is provided and includes a mounting plate integrally formed with one end of the drive shaft, the mounting plate having an inclined surface. The rocker mechanism further includes a flat plate mounted in abutting relationship with the mounting plate inclined surface, and a linkage arm operatively coupling the flat plate and the piston.  
      One aspect of the present invention is the in at least one embodiment, the wobble plate of the prior art is eliminated. This may be particularly advantageous in the production of the compressor, reducing the number of parts and thus the cost of manufacturing.  
      Another advantage is of the present invention is that the pistons of the reciprocating piston compressor are mounted directly to means for linking the mounting plate and the piston, the means including a bearing, flat plate, or inclined plate. The use of a ball joint or roller bearing to mount the bearing, flat plate, or inclined plate of the present invention has been eliminated.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The above mentioned and other features and objects of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:  
       FIG. 1  is a sectional view of a reciprocating piston compressor in accordance with a first embodiment of the present invention showing a first position of the compression mechanism.  
       FIG. 2  is a sectional view of the compressor of  FIG. 1  showing a second position of the compression mechanism.  
       FIG. 3  is a sectional view of a reciprocating piston compressor in accordance with a second embodiment of the present invention showing a first position of the compression mechanism.  
       FIG. 4  is a sectional view of the compressor of  FIG. 3  showing a second position of the compression mechanism.  
       FIG. 5  is a sectional view of a reciprocating piston compressor in accordance with a third embodiment of the present invention showing a first position of the compression mechanism.  
       FIG. 6  is a sectional view of the compressor of  FIG. 5  showing a second position of the compression mechanism.  
       FIG. 7  is an exploded sectional view of the assembly of the rocker mechanism of the compressor of  FIG. 5 .  
       FIG. 8  is a top view of the mounting plate of the drive shaft of  FIG. 7  taken along line  8 - 8 . 
    
    
      Corresponding reference characters indicate corresponding parts throughout the several views. Although the exemplification set out herein illustrates embodiments of the invention, in several forms, the embodiments disclosed below are not intended to be exhaustive or to be construed as limiting the scope of the invention to the precise forms disclosed.  
     DETAILED DESCRIPTION  
      In general, a reciprocating piston compressor is one in which the linear, reciprocating motion of one or more pistons within a cylinder compresses a working fluid such as a refrigerant from a low pressure to a higher pressure. Reciprocating piston compressors may be used in any suitable refrigeration or air-conditioning system (not shown).  
      The general structure and operation of a reciprocating piston compressor is discussed with reference to the first embodiment of reciprocating piston compressor  20 , however, it is understood that the general structure and operation is the same for all embodiments discussed herein. Referring to  FIGS. 1 and 2 , reciprocating piston compressor  20  is a hermetic compressor assembly including housing  22  having main body portion  23  to which top end cap  24  and bottom end cap  26  are secured. End caps  24  and  26  are fixedly secured to housing main body portion  23  by any suitable method including welding, brazing, or the like so as to create a hermetically sealed environment within housing  22 . Annular mount  28  is affixed to the lower surface of bottom end cap  26  by any suitable method to support compressor  20  in a substantially horizontal orientation.  
      Reciprocating piston compressor  20  is provided with drive motor  30  which includes stator  32  having windings  34 , and rotor  36 . Stator  32  is positioned in surrounding relationship of rotor  36  and is interference fitted within housing  22 . Electrical current from an external power source (not shown) is directed through stator windings  34  via a terminal cluster (not shown) to electromagnetically induce rotation of rotor  36 . Drive shaft  38  extends longitudinally through central aperture  40  in rotor  36  and is operatively connected to compression mechanism  42  in a manner which will be described further below.  
      Compression mechanism  42  is mounted above motor  30  and includes cylinder block  44  which is interference fitted within main body portion  23  of housing  22 . At least one cylinder  46  is bored into cylinder block  44  with one piston  48  being reciprocatively positioned in each cylinder  46 . In this embodiment, drive shaft  38  is operatively coupled to a pair of pistons  48 ′ and  48 ″ such that as drive shaft  38  is caused to rotate by rotation of rotor  36 , refrigerant is drawn into cylinders  46  where it is compressed before being discharged to the refrigeration system, for example.  
      During compressor operation, refrigerant at suction pressure is drawn into housing  22  through an inlet (not shown). Compressor  20  is a low-side compressor with drive motor  30  being in a low pressure and low temperature environment. Alternatively, compressor  20  may also be a high side compressor with the motor being located in a high pressure and high temperature environment. Referring to  FIG. 1 , the suction pressure refrigerant is directed toward cylinders  46  and is drawn into cavity  50  defined in one cylinder  46  when piston  48 ′ is on a downward stroke. With cavity  50  filled with suction pressure refrigerant ( FIG. 2 ), piston  48 ′ begins its upward stroke, reducing the volume of cavity  50  and compressing the refrigerant located therein. The compressed refrigerant has a high, discharge pressure as piston  48 ′ completes the upward stroke. The discharge pressure is great enough to overcome the biasing force of discharge valve  52  allowing the discharge pressure refrigerant gas to pass through discharge outlet  54  into cylinder head  56  mounted to cylinder block  44 . The discharge pressure refrigerant then exits compressor  20  and flows into the refrigeration system.  
      The second piston  48 ″ is 180 degrees out of phase from the first piston  48 ′ such that as piston  48 ′ is compressing refrigerant in cavity  50 , piston  48 ″ is on a downward stroke drawing suction pressure refrigerant into cavity  58  defined in cylinder  46 . Once cavity  58  is filled with suction pressure refrigerant, piston  48 ″ begins an upward stroke, compressing the refrigerant to a higher, discharge pressure. The discharge pressure is great enough to overcome the biasing force of discharge valve  52  operatively associated with discharge outlet  54 , thus allowing the discharge pressure refrigerant to exit compressor  20  and flow into the refrigeration system.  
      Drive shaft  38  is operatively connected to compression mechanism  42  by rocker mechanism  60  which converts rotational motion of drive shaft  38  into linear, reciprocating motion of pistons  48 . Rocker mechanism  60  includes mounting plate  62  integrally formed at the end of drive shaft  38 . Mounting plate  62  includes first height  63  and second height  65  with the first height  63  being greater than the second height  65  to define inclined surface  64  on which bearing  66  of rocker mechanism  60  is fixedly mounted.  
      Annular supporting plate  68  is mounted above drive motor  30  by bolts  70 . A first nut  72  threadedly engages each bolt  70  to support supporting plate  68 . A second nut  74  is threaded onto each bolt  70  to secure the position of supporting plate  68 . The height of supporting plate  68  may be adjusted as necessary by raising or lowering first nuts  72  along bolts  70 . Integrally formed in supporting plate  68  is hub  76  through which drive shaft  38  extends and is rotatably supported by bearing  78 . A second bearing  80  is located between lower surface  82  of mounting plate  62  and upper surface  84  of supporting plate  68 .  
      Bearing  66  is a ball bearing including inner race  86  and outer race  88 . A plurality of ball bearings  90  are located between inner and outer races  86  and  88  being seated in grooves  92  and  94  respectively formed in the races. Outer race  88  is fixedly secured to mounting plate  62  by a plurality of fasteners  96  such that outer race  88  rotates with drive shaft  38 . Inner race  86  is secured to pistons  48  by linkage arms  98 . Linkage arms  98  fix the position of inner race  86  relative to outer race  88  such that inner race  86  does not rotate.  
      The diameter of bearing  66  is determined by the spacing between first and second pistons  48 ′ and  48 ″ with the diameter of inner race  86  being substantially equal to the distance between the centers of the pistons. The length of the piston stroke is defined by the degree of incline of surface  64 . With outer race  88  located about the outer periphery of mounting plate  68 , the stroke of pistons  48 ′ and  48 ″ is at its greatest length such that the greater the degree of incline, the longer the stroke of the pistons.  
      During operation of compressor  20 , drive shaft  38  rotates causing mounting plate  62  and thus outer race  88  of bearing  66  to rotate. Referring to  FIG. 1 , as mounting plate  62  rotates, the portion of mounting plate  62  having first height  63  forces piston  48 ′ to the top end of the upward stroke. Simultaneously, piston  48 ″ is aligned with the portion of mounting plate  62  having second height  65  and bottoms out at the end of its downward stroke. As mounting plate  62  continues to rotate pistons  48 ′ and  48 ″ reciprocate within cylinders  46  to a position shown in  FIG. 2  wherein piston  48 ′ is aligned with the portion of mounting plate  62  having second height  65  and at the end of its downward stroke and piston  48 ″ is aligned with the portion of mounting plate  62  having first height  63  and at the end of its upward stroke.  
      Also during compressor operation, oil from oil sump  100  defined by the lower end of housing main body portion  23  and bottom end cap  26  is drawn through bore  102  formed in drive shaft  38  to lubricate inclined surface  64 . The lubricating oil is also supplied to the surfaces of bearings  78  and  80  through radial passages (not shown) in drive shaft  38 .  
      Referring to  FIGS. 3 and 4 , a second embodiment of a reciprocating compressor is illustrated. Reciprocating compressor  104  is a single piston compressor having piston  48  slidingly mounted in cylinder  46 . Compressor  104  operates in a manner similar to that described above with regards to compressor  20 . Suction pressure refrigerant is drawn into cylinder  46  when piston  48  is on the downward stroke. When piston  48  returns to its upward position, the suction pressure refrigerant is compressed to a higher, discharge pressure before exiting compressor  104  into a refrigeration system, for example.  
      In this embodiment, drive shaft  38  is operatively coupled to compression mechanism  105  by rocker mechanism  106  which converts rotational motion of drive shaft  38  into linear, reciprocating motion of piston  48 . Rocker mechanism  106  includes mounting plate  108  and actuating plate  110 . Mounting plate  108  has a first height  112  and a second height  114  with the first height being larger than the second height to define inclined surface  116 . Actuating plate  110  also includes a first height  118  and a second height  120  with the first height being larger than the second height to define inclined surface  122 . Mounting plate  108  is integrally formed at the end of drive shaft  38  for rotation therewith. Piston  48  has rod  124  secured to the lower end thereof. Actuating plate  110  is a non-rotating plate which is fixedly mounted to rod  124  by any suitable method including welding, brazing, or the like, thus actuating plate  110  moves linearly as mounting plate  108  rotates.  
      A first annular supporting plate  126  is located above motor  30  being supported on bolts  128  engaging motor  30  by first and second nuts  130  and  132 . As discussed above, the location of supporting plate  126  is adjustable by moving nuts  130  and  132  along the length of bolts  128 . A second annular plate  134  is mounted on bolts  128  in a position above rocker mechanism  106  by first and second nuts  136  and  138 .  
      First annular supporting plate  126  is provided with opening  140  in which drive shaft  38  is rotatably supported by bearing  142 . Bearing  144  is positioned between lower surface  146  of mounting plate  108  and upper surface  148  of first annular supporting plate  126  to rotatably support mounting plate  108 . Bearing  142  is provided with protrusions  150  which lock the bearing in place between drive shaft  38  and first annular supporting plate  126 . Second annular supporting plate  134  is provided with opening  152  through which rod  124  passes. Second annular supporting plate  134  is provided to support rod  124  as piston  48  reciprocates within cylinder  46 .  
      Rod  124  passes through actuating plate  110  and is slidingly received in central cavity  154  passing through mounting plate  108  and into drive shaft  38 . Central passageway  156  is located in rod  124  and aligns with bore  102 . As drive shaft  38  rotates and oil is drawn upwardly along bore  102 , the oil enters cavity  154  and central passageway  156  to provide lubrication to interfacing inclined surfaces  116  and  122  as well as between rod  124  and the inner surface of central cavity  154 . As in the previous embodiment, oil is also provided to the surfaces of bearing  142  and  144  through radial passages (not shown) in drive shaft  38 .  
      During operation of compressor  104 , drive shaft  38  rotates causing mounting plate  108  to rotate. Referring to  FIG. 3 , in the first position, piston  48  is at the bottom end of cylinder  46  and inclined surfaces  116  and  122  are engaged. As mounting plate  108  rotates to a second position shown in  FIG. 4 , the portion of mounting plate  108  having first height  112  aligns with the portion of actuating plate  110  having first height  118 , forcing piston  48  to the top end of the upward stroke and compressing refrigerant in cylinder  46 . Rod  124  slides upwardly in central cavity  154  pulling oil from bore  102  along the inner surface of central cavity  154  to lubricate the cavity.  
      Referring to  FIGS. 5 and 6 , a third embodiment of a reciprocating piston compressor is shown. Reciprocating piston compressor  158  is a two piston compressor similar to compressor  20  of the first embodiment. Drive shaft  38  is operatively coupled to compression mechanism  159  by rocker mechanism  160  which converts the rotation motion of drive shaft  38  into linear motion of pistons  48 ′ and  48 ″. Rocker mechanism  160  includes mounting plate  162  having first height  164  and second height  166  with first height  164  being greater than second height  166  to define inclined surface  168 . Drive shaft  38  passes through annular supporting plate  68  which is mounted within housing  22  above motor  30  in the same manner as described above. Bearings  78  and  80  are positioned between drive shaft  38 , supporting plate  68 , and mounting plate  162  to rotatably support drive shaft  38  and thus mounting plate  162 .  
      Compression mechanism  159  is provided with cylinder block  170  in which cylinders  46  are formed to receive pistons  48 ′ and  48 ″. Cylinder head  172  is mounted to the upper surface of cylinder block  170  having discharge valves  174  mounted therein. Discharge valves  174  include valve plates  176  which are biased by springs  178  into a closed position over cylinders  46 . One end of springs  178  is located in cavities  180  formed in cylinder head  172  while the opposite end of springs  178  are in engagement with upper surface  182  of valve plates  176 . Valve passage  184  is formed in cylinder block  170  and has a diameter slightly larger than the diameter of cylinders  46  so that refrigerant cannot leak past valve plates  176 . Discharge passages  186  are also formed in cylinder block  170  to provide passages for compressed discharge pressure refrigerant into the refrigeration system.  
      Rocker mechanism  160  further includes flat plate  188  which is non-rotatably mounted in abutting relationship to inclined surface  168  of mounting plate  162 . Referring to  FIGS. 5, 6 , and  7 , retaining clip  190  is used to secure flat plate  188  to mounting plate  162 . Retaining clip  190  includes spherical end  192  and at least two legs  194  having protrusions  196  located at the end thereof for locking clip into place. Retaining clip  190  may be provided with any suitable number of legs  194  required to secure flat plate  188  in an assembled position with mounting plate  162 . Located centrally in flat plate  188  is concave seat  198  in which spherical end  192  of clip  190  is seated. Retaining clip  190  is formed of a semi-rigid plastic material, for example, having resilient properties that allow legs  194  to move inwardly as retaining clip  190  is installed. Legs  194  pass through passage  200  in flat plate  188  and through a portion of bore  102  in drive shaft  38  into cutout portion  202  in drive shaft  38 . Once protrusions  196  reach cutout portion  202 , legs  194  return to their initial position and protrusions  196  engage surface  204  of cutout portion  202  to lock flat plate  188  against mounting plate  162 .  
      Integrally formed on upper surface  190  of flat plate  188  is a protrusion  206  having a semispherical cross-section. Protrusion  206  is located about the periphery of flat plate  188  and has a diameter equal to the distance between the centers of pistons  48 ′ and  48 ″. Linkage arms  208  extend between protrusion  206  and pistons  48 ′ and  48 ″ to operatively connect drive shaft  38  to compression mechanism  159 . One end of linkage arms  208  are provided with convex shaped cavity  210  into which protrusion  206  is seated. The opposite end of linkage arms  208  include spherical ends  212  which are received in pistons  48 ′ and  48 ″. Springs  213  are located between cylinder block  170  and surface  209  of linkage arms  208  to bias arms  208  into contact with protrusions  206 , particularly during compressor startup.  
      During operation of compressor  158 , drive shaft  38  rotates causing mounting plate  162  to rotate. Referring to  FIG. 5 , as mounting plate  162  rotates, the portion of mounting plate  62  having first height  164  forces piston  48 ′ to the top end of the upward stroke. This compresses refrigerant in cylinder  46  to a higher discharge pressure which is great enough to overcome the biasing force of spring  178 , moving valve plate  176  from its seated position and allowing the refrigerant to exit compressor  158 . Simultaneously, piston  48 ″ is aligned with the portion of mounting plate  162  having second height  166  and bottoms out at the end of its downward stroke. As mounting plate  162  continues to rotate, flat plate  188  rides along inclined surface  168 , pivoting about spherical end  192  of retaining clip  190 . Pistons  48 ′ and  48 ″ reciprocate within cylinders  46  to a position shown in  FIG. 6  wherein piston  48 ′ is aligned with the portion of mounting plate  162  having second height  166  and at the end of its downward stroke and piston  48 ″ is aligned with the portion of mounting plate  162  having first height  164  and at the end of its upward stroke.  
      Also during compressor operation, as with previous embodiments, oil from oil sump  100  defined by the lower end of housing main body portion  23  and bottom end cap  26  is drawn through bore  102  formed in drive shaft  38  to lubricate inclined surface  168 . As shown in  FIG. 8 , inclined surface  168  is provided with curved grooves  214  which direct the lubricating oil toward the outer periphery of mounting plate  162  to provide lubricating oil to the interfacing surfaces between mounting plate  162  and flat plate  188 . The lubricating oil is also supplied to the surfaces of bearings  78  and  80  through radial passages (not shown) in drive shaft  38 .  
      While this invention has been described as having an exemplary design, the present invention may be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles.