Patent Publication Number: US-6908290-B2

Title: Air conditioning compressor having reduced suction pulsation

Description:
TECHNICAL FIELD OF THE INVENTION 
     This invention relates to a compressor for an automotive air conditioning system. More particularly, this invention relates to such compressor that includes a suction chamber that is configured to reduce pressure pulsations in refrigerant that is supplied to the compressor. 
     BACKGROUND OF THE INVENTION 
     An air conditioning system, such as for an automotive vehicle, comprises a compressor that delivers compressed refrigerant to a condenser, wherein heat is extracted from the refrigerant. The refrigerant flows from the condenser to an evaporator that expands the refrigerant to extract heat from the ambient. The spent refrigerant is recycled from the evaporator to the compressor. The compressor typically comprises pistons that reciprocate within cylinder chambers to draw in the spent refrigerant, compress the refrigerant, and discharge the compressed refrigerant to the condenser. Within the compressor, the refrigerant travels through a head that includes a suction chamber for supplying spent refrigerant to the cylinders and a discharge chamber that receives the compressed refrigerant. Suction ports with valves regulate refrigerant flow from the suction chamber to the cylinder chambers, whereas discharge ports with valves regulate refrigerant flow from the cylinder chambers to the discharge chamber. 
     The refrigerant within the suction chamber exhibits a relatively low pressure within the system. During the suction stroke, the piston is withdrawn to increase the volume within the cylinder chamber, and the valve opens to admit refrigerant through the suction port. Refrigerant flow into the cylinder chamber produces a temporary drop in the pressure of suction-side refrigerant. As each piston successively cycles through the suction stroke, the result is a regular fluctuation in suction-side pressure, referred to as pressure pulsation. This pressure pulsation is noticeable not only within the suction chamber, but also through the line to the evaporator, and results in vibration and increased noise within the system. Moreover, there is a desire to reduce the number of pistons within the compressor to thereby reduce cost and weight. However, pressure pulsation becomes more noticeable as the number of pistons is reduced, thereby increasing the associated flow-induced vibration and noise problems. 
     Therefore, a need exists for a compressor for an automotive air conditioning system having a suction chamber that confines pressure pulsation and thereby minimizes propagation of flow-induced vibration and noise through the suction-side components. 
     BRIEF SUMMARY OF THE INVENTION 
     This invention provides a compressor for an automotive air conditioning system that includes a cylinder block defining a plurality of cylinder chambers and pistons reciprocately received in the cylinder chambers. The compressor also includes a cylinder head that comprises a suction chamber and discharge chamber. Suction ports communicate between the cylinder chambers and the suction chamber for admitting refrigerant from the suction chamber into the cylinder chamber. Discharge ports communicate between the cylinder chambers and the discharge chamber for discharging refrigerant from the cylinder chambers to the discharge chamber. In accordance with this invention, the cylinder head comprises a first annular wall defining a mixing chamber and a second annular wall disposed about the first annular wall and spaced apart therefrom to define the suction chamber. The discharge chamber is disposed about the second annular wall. An inlet is provided for supplying refrigerant to the mixing chamber. Preferably, fluid flows through the mixing chamber in a swirling or other turbulent pattern to provide a more uniform pressure through the upstream components. The first annular wall that divides the mixing chamber from the suction chamber includes at least two openings in circumferentially spaced relationship for passing fluid from the mixing chamber to the suction chamber. By providing the mixing chamber and isolating the mixing chamber from the suction chamber by the first annular wall, pressure pulsation resulting from opening of the suction ports to admit refrigerant from the suction chamber to the cylinder chambers is confined to the suction chamber, and pulsation propagation through the mixing chamber to other suction-side components is reduced. This reduces flow-induced vibration and noise within the automotive air conditioning system. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       This invention will be further illustrated with reference to the accompanying drawings wherein: 
         FIG. 1  is a cross-section of an air conditioning compressor in accordance with a preferred embodiment of this invention; 
         FIG. 2  is a cross-section of the air conditioning system in  FIG. 1  taken along lines  2 — 2  in the direction of the arrows; and 
         FIG. 3  is a view showing a head in accordance with an alternate embodiment of this invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In accordance with a preferred embodiment of this invention, referring to  FIGS. 1 and 2 , there is depicted a rear portion of a compressor  10  adapted for an automotive air conditioning system to compress a refrigerant. Suitable refrigerants include organic compounds, such as refrigerant designated R134. Alternately, this invention may be used with carbon dioxide refrigerant, which require higher pressures that result increased vibration and noise due to suction-side pulsation. Compressor  10  has a central longitudinal axis  11  and comprises a cylinder head  12 , which may be part of a rear housing section. Cylinder head  12  defines a plurality of cylinder chambers  14  coaxial to axis  11 . In the described embodiment, cylinder block  12  includes five cylinder chambers equal angularly spaced about axis  11 . However, this invention may be utilized with compressors that included 3, 4 or any suitable number of cylinders. Pistons  16  are slideably received in cylinder chambers  14  and are reciprocated by a swashplate mounted on a shaft, which is in turn driven by the automotive engine through a belt and pulley mechanism. A suitable swashplate mechanism is described in U.S. Pat. No. 6,318,972, incorporated herein by reference. During operation, each piston  16  reciprocates to retract the piston to draw relatively low pressure refrigerant into the cylinder chamber and to advance the piston to compress the refrigerant and discharge compressed refrigerant from the cylinder chamber. The motion of the multiple pistons is sequenced by the swashplate mechanism, so that some pistons are being withdrawn while others are being advanced, thereby providing an continuous flow of refrigerant through the air conditioning compressor. In  FIG. 1 , the piston is depicted in a stage of being withdrawn to suck refrigerant into the cylinder chamber. 
     Compressor  10  also comprises a rear head  20  for supplying refrigerant to the cylinder chambers and receiving compressed refrigerant therefrom. In the described embodiment, rear head  20  includes an internally threaded collar  21  for mounting onto cylinder head  12 . A valve plate  22  is interposed between cylinder head  12  and the refrigerant chambers within rear head  20 . Valve plate  22  defines suction ports  24  for admitting refrigerant to cylinder chambers  14  and discharge ports  26  for discharging compressed refrigerant therefrom. A flexible membrane  28  overlying valve plate  22  adjacent cylinder head  12  is cut to define reed valves  30  to regulate refrigerant flow through suction ports  24 . Similarly, a flexible membrane  32  overlying valve plate  22  opposite cylinder head  12  defines reed valves  34  to regulate refrigerant flow through discharge ports  26 . 
     In accordance with this invention, the rear head includes a pattern of walls that define chambers for conveying refrigerant. In particular, head  20  comprises a first annular wall  38  that cooperates with an end wall  40  to define a mixing chamber  42 . Refrigerant is admitted to mixing chamber  42  through an inlet passage  44  that is externally connected to a tube leading from an evaporator. Refrigerant enters chamber  42  through an opening  46 . In the preferred embodiment, opening  46  is offset from the center of the mixing chamber, which corresponds to axis  11 , and directs flow toward a deflector  47 . The offset arrangement of opening  46  and deflector  47  creates a swirling flow of refrigerant within mixing chamber  42  which facilitates the mixing of refrigerant, thereby providing a more uniform pressure and reducing pulsations within the suction-side fluid. 
     Rear head  20  also includes a second annular wall  50  generally cylindrical about axis  11  and spaced outboard from first annular wall  38  to define a suction chamber  52  therebetween. Ports  54  in first annular wall  38  provide refrigerant flow from mixing chamber  42  into suction chamber  52 . It is a feature of this embodiment that ports  54  are axially displaced from opening  46  to enhance swirling flow of refrigerant through mixing chamber  42  and provide a more uniform mixture to suction chamber  52 . Suction ports  24  to cylinder chamber  14  are located to communicate with suction chamber  52 , as indicated by the dashed lines in  FIG. 2. A  wall  56  extends radially through suction chamber  52  to block circumferential propagation of pressure pulsations within suction chamber  52 . During operation, pistons  16  draw refrigerant from suction passage  52  in a circumferential sequence, opening the inlet valves and creating a pressure pulse in the region adjacent the suction port. Wall  56  limits the pulses accumulating beyond a single revolution and thereby reduces the amplitude of the pressure pulsations and the associated flow-induced vibration and noise. In addition, wall  38  limits communication between mixing chamber  42  and suction chamber  52  and thus isolates pressure pulsations within suction chamber  52  from mixing chamber  42 . This reduces propagation of pulsations through inlet passage  44  to other components of the air conditioning system. 
     Head  20  further includes an outer wall  60  spaced apart from wall  50  to define discharge chamber  62 . Discharge ports  26  from cylinder chambers  14  are located to communicate with discharge chamber  62 , as indicated by the dashed lines in FIG.  2 . From discharge chamber  62 , refrigerant flows through a discharge port  64  to an outlet passage  65 . Passage  65  includes an oil separator (not shown) to recapture excess lubricant from the discharged refrigerant. The oil separator also serves as a muffler to restrict propagation of discharge-side pressure pulsations out of head  64  to other components. Discharge passage  64  is coupled to a tube that leads to the condenser of the air conditioning system. 
     Head  20  includes bores  70  for bolting the rear head to the other housing sections, and bore  72  for receiving a bolt to mount compressor  10  to the vehicle. Also, a chamber  74  is provided for enclosing a control valve assembly (not shown). 
     During operation, spent refrigerant from the evaporator is conveyed through a tube to inlet passage  44  and admitted through opening  46  into mixing chamber  42 . The offset arrangement of opening  46  and deflector creates a swirling flow of refrigerant through the mixing chamber to minimize pressure variations therein. Refrigerant flows radially through ports  54  into suction chamber  52 . As piston  16  is withdrawn from valve plate  22  to expand the volume within cylinder chamber  14 , refrigerant flows from suction chamber  52  through suction port  24  into the cylinder chamber, with valve  30  opening to admit the fluid. Thereafter, as piston  16  travels toward valve plate  22  to compress the refrigerant, valve  30  closes, and valve  36  opens to expel the compressed fluid into discharge chamber  62 . Refrigerant flows from discharge chamber  62  through discharge port  64  and passage  65 , and is output from the compressor to a tube en route to the condenser. 
     Thus, this invention provides an arrangement of refrigerant chambers wherein the refrigerant is input to a mixing chamber and radially distributed to a suction chamber that is separated by a wall. Pressure pulsation caused by withdrawal of fluid by the cylinder chambers occur within the suction chamber and are restricted from propagation to the mixing chamber. Thus, the mixing chamber provides a barrier to pulsation propagation to external components. By locating the suction chamber inward from the discharge chamber, suction pulsation is further confined within the rear head, thereby further reducing associated vibration and noise. Thus, this invention provides a compressor wherein flow-induced noise and vibration attributed to suction-side pulsation is reduced. Moreover, the preferred embodiment includes a radial wall to block circumferential travel of pulsation through the suction chamber and thereby reduce the amplitude of the pulsation within the suction chamber. 
     In the embodiments depicted in  FIGS. 1 and 2 , a single radial wall is provided to block circumferential propagation of pulsations. Nevertheless, the amplitude of pulsations is permitted to build up through the suction chamber prior to the wall. Referring now to  FIG. 3 , there is depicted an alternate embodiment of this invention that includes multiple radial walls within the suction chamber to further confine pulsations to limited regions. In  FIG. 3 , like numerals are employed to represent elements common to the embodiment in  FIGS. 1 and 2 . A rear head  100  comprises a first annular wall  102  that defines a central mixing chamber  104 , and a second annular wall  106  that encircles first annular wall  102  and spaced apart therefrom to define a suction chamber  108 . Refrigerant is delivered to mixing chamber  104  through inlet passage  110 , which is offset relative to axis  11  to create a swirling flow pattern. Refrigerant is distributed from mixing chamber  104  to suction chamber  108  through openings  111  and  112  and passage  113 . Multiple walls  114 ,  116  and  118  extend generally radially to divide suction chamber  108  into sub-chambers. In this example, wherein the compressor comprises five cylinder chambers, suction chamber  108  communicates with suction ports to two pistons through opening  111 , with the suction ports to two other cylinder chambers through opening  112 , and with the remaining one cylinder chamber through passage  113 . Thus, pressure pulsation created by the two cylinder chambers is isolated to regions of the suction chamber that communicate with no more than two cylinder chambers. Head  100  further comprises an outer wall  120  that is disposed about the second annular wall  106  and spaced apart therefrom to define a discharge chamber  122 , in a manner similar to the embodiments in  FIGS. 1 and 2 . In this manner, discharge chamber  122  isolates suction chamber  108  from the outer wall  120  to confine suction-side pulsation within the center of the head. As in the first described embodiment, head  100  provides a mixing chamber with a swirling flow pattern to provide a more uniform pressure within the fluid within the head and thereby alternate pressure pulsation. 
     In the embodiment in  FIG. 3 , radial walls were arranged to divide the suction chamber into subchambers such that each subchamber communicates with no more than 2 cylinder chambers. Alternately, walls may be arranged to form subchambers that communicate with single cylinder chambers, or with 2 and 3 cylinder chambers. 
     While this invention has been described in terms of certain embodiments thereof, it is not intended to be so limited, but rather only to the extent set forth in the claims that follow.