Patent Publication Number: US-2009232667-A1

Title: Axial compressor

Description:
This invention claims benefit of Provisional Application No. 60/830,374, filed Jul. 12, 2006. 
    
    
     GOVERNMENT RIGHTS 
     This invention was made with Government support under Contract No. DAAB15-02-C-0006 awarded by USA CECOM Acquisition Ctr-Washington. The Government has certain rights in the invention. 
    
    
     I. BACKGROUND OF THE INVENTION 
     This invention relates to fluid compression and fluid transfer mechanisms for an axial fluid displacement apparatus. More particularly, it relates to a configuration of a bearing supported wobble plate plus intake and discharge valve mechanisms for a reciprocating piston, wobble plate-type refrigerant compressor suitable for use with high pressure CO 2  as a working refrigerant. 
     Piston-type compressors, such as swash plate-type compressors and wobble plate-type compressors are known in the art. 
     The challenges of lubricating piston-type compressors which utilize carbon dioxide as a refrigerant are known in the art. 
     The use of higher pressures in both the high pressure output side and low pressure input side sections of a refrigeration system that utilizes carbon dioxide as the refrigerant are known in the art. 
     II. SUMMARY OF THE INVENTION 
     With reference to  FIG. 1 , a wobble plate-type compressor is shown comprising a compressor housing  01  having a cylinder block  02  fixed at the rear end of compressor housing  01 . A cylinder head  03 , defining a discharge chamber  04  and intake chamber  05  is mounted on the rear end opening of compressor housing  01  behind a valve plate  06 . In the instant invention, the motor  07 , drive shaft  08 , wobble plate  09 , cylinder barrel  10  and pistons  11  are hermetically sealed in compressor housing  01 . It will be obvious to one skilled in the art to separate the motor  07  and the compressor housing  01 . 
     A discharge valve assembly is mounted on a rear end surface of valve plate  06 . Valve plate  06  has a discharge hole  12  extending there through to allow communication between the compression chamber  13  and discharge chamber  04 . The discharge valve assembly comprises a discharge valve  14  and a valve retainer  15 , which is secured to a rear end surface of valve plate  06 . In the instant invention, discharge valve  14  is fabricated from a single sheet of material. It will be obvious to one skilled in the art, that other means of fabricating discharge valves and securing their position over cylindrical bore  16  are possible. 
     Referring to  FIG. 1 , valve retainer  15  limits the bending movement of discharge reed valve  14  in the direction in which the refrigerant gas exits a cylindrical bore  16  and enters discharge chamber  13  through discharge hole  12 . Discharge reed valve  14  has a modulus of elasticity which keeps discharge hole  12  closed until the pressure in cylinder bore  16  reaches a predetermined value. 
     Referring to  FIG. 1 , intake port  17  in the side of cylindrical bore  16  allows communication between the compression chamber  13  and the intake chamber  05 . At or about bottom-dead-center of piston  11  stroke, intake port  17  is open to the intake chamber  05 . When refrigerant pressure in the intake chamber  05  exceeds the pressure within the compression chamber  13 , refrigerant is injected into the compression chamber  13  through intake port  17 . As piston  11  begins its travel to the top of compression chamber  13 , it covers intake port  17  and seals the compression chamber  13 . It will be obvious to one skilled in the art to change the location distance of the intake port from top-dead-center of the cylindrical bore, the size of the intake port or both to optimize the efficiency of the refrigerant compressor. 
     Compressor housing  01  defines a center bearing crank chamber  18  that is adjacent to cylinder block  02 . Cylinder block  02  is provided with a plurality of equi-angularly spaced cylindrical bores  16 . A drive shaft  08  is rotatably supported at its rear end by compressor housing end block  19  and bearing  20 , and at its front end through a wobble plate  09  which is itself captured by a thrust bearing  21  and a tapered roller bearing  22  while being driven by the motor shaft  08  to which it is keyed. Wobble plate  09  is prevented from axial and longitudinal movement by use of roller bearings  21  and  22  while permitting free rotational movement of the wobble plate. A reciprocating piston  11  is received in each of cylindrical bores  16 . Each piston  11  is held in contact to a slipper plate  30  with piston shoe  23 . A retainer ring  24  is loaded against the shoe  23  flange by spring  25  and spherical ball seat  26  thus holding the pistons against the slipper plate  30 . The slipper plate  30  is separated from the wobble plate  09  by a thrust bearing  29 ; thus, the slipper plate  30  wobbles but does not rotate even as the wobble plate  09  spins rapidly under it. This precludes the piston shoes  23  having to slide frictionally over the face of a spinning wobble plate  09 . It will be obvious to one skilled in the art that the load spring assembly can be replaced by gas springs to maintain proper piston shoe contact with the wobble plate. 
     It will be obvious to one skilled in the art that the use of roller bearings, ball bearings or both to support the wobble plate will enhance lubrication of rotating surfaces in the presence of carbon dioxide which is known to dilute compressor lubricants over time until too thin to sustain plain bearing loads. 
     III. OBJECTS AND ADVANTAGES 
     It is an object of the present invention to provide a piston-type fluid displacement apparatus which prevents the problem of lubrication of piston compressors for carbon dioxide refrigerant caused by dilution of lubricant by the refrigerant. 
     It is another object of the present invention to provide a piston-type fluid displacement apparatus which utilizes roller bearings, ball bearings or both to prevent axial and longitudinal movement of the wobble plate while permitting free rotational movement of the wobble plate. 
     It is another object of the present invention to provide a piston-type fluid displacement apparatus which utilizes the high pressure refrigerant in the suction side to inject refrigerant into the cylinder bore through a side intake port at or about bottom-dead-center position of the piston. 
     It is another object of the present invention to provide a piston-type fluid displacement apparatus which utilizes a common discharge reed valve plate to control discharge of refrigerant from the cylinder bore. 
     It is a further object of the present invention to provide a piston-type fluid displacement apparatus which comprises roller bearings, ball bearings, or both to prevent axial and longitudinal movement of the wobble plate while permitting free rotational movement of the wobble plate, a common discharge reed valve plate to control discharge of refrigerant from the cylinder bore and an intake port in the side of the cylinder bore to allow injection of refrigerant into the cylinder bore at or about bottom-dead-center position of the piston. 
     Further objects, features, and advantages of this invention will be understood from the attached drawings. 
    
    
     
       IV. BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of a wobble plate-type refrigerant compressor in accordance with a known embodiment. 
         FIG. 2  is a schematic diagram of an output valve plate in accordance with a known embodiment. 
         FIG. 3  is a schematic diagram of an output reed valve in accordance with a known embodiment. 
     
    
    
     V. DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to  FIG. 1 , there is illustrated a hermetically sealed, multi-cylinder axial refrigerant compressor. The compressor is contained within a main housing or case  01  having a top or front end  19  and a rear end  27 . Case bolts  28  extend through the main housing  01  to secure the housing and its components yet allow access to the components when required. A drive shaft  08  spins a wobble plate  09 . The cylinder barrel  02  contains at least one compression cylinder  10 . The cylinder  10  has a head end  03  adjacent to the rear end  27 . There is a piston foot  23  at one end of each of the pistons opposite the head end  03  with the other end of each piston extending into each of the cylinders  10 . The pistons  11  cycle as the wobble plate  09  is spun by the drive shaft  08 . Near the rear end  03  of the cylinder  10  is a fixed valve plate  06 . 
     The compression cycle operates as in a conventional axial compressor. The cylinders  10  and pistons  11  are disposed circumferentially about the drive shaft  08  within the cylinder barrel  02 . There are piston cylinder discharge ports  12  in the head end  03  of the cylinder  10  that are open to and communicate with the discharge chamber  04 . During operation of the compressor, an intake charge is injected through the intake port  17  and a high pressure charge is delivered at the discharge port  12 . Movement of the piston  11  opens and closes communication between the compression chamber  13  and the intake chamber  05 . Communication between the compression chamber  13  and the discharge chamber  04  is controlled by valve plate  06  and valve  14 . 
     Thus there has been provided a reciprocating piston, wobble plate-type refrigerant compressor that fully satisfies the objects set forth above. While the invention has been described in conjunction with a specific embodiment, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications and variations as fall within the spirit and scope of the appended claims.