Abstract:
An oil separator for a compressor is shown, wherein an oil separating efficiency is maximized and a material cost, a weight, and an assembly time are minimized.

Description:
FIELD OF THE INVENTION 
     The present invention relates to an oil separator and more particularly to an oil separator for a fluid displacement apparatus wherein oil separation capabilities are maximized. 
     BACKGROUND OF THE INVENTION 
     Compressors used in refrigeration and air conditioning systems such as swashplate type compressors, for example, typically include a lubricating oil mist suspended in a gaseous refrigerant medium. Such compressors also include a first path that provides refrigerant communication between the crank chamber and the discharge chamber, and a second path that provides refrigerant communication between the crank chamber and the suction chamber. 
     During operation of the compressor, the oil mist lubricates the moving parts of the compressor. However, oil that remains suspended in the refrigerant as it travels throughout the refrigeration circuit can reduce the performance of the refrigeration circuit. Also, by reducing oil available to the moving parts of the compressor, the compressor is susceptible to increased wear and seizure potential. 
     To combat these problems, an oil separator can be added to the refrigeration circuit. Such an oil separator is typically positioned between the compressor outlet and a condenser inlet. The oil separator functions to separate the suspended oil from the gaseous refrigerant, so that the oil is maintained in the compressor and not introduced into the suction chamber. 
     It would be desirable to produce an oil separator wherein an oil separation efficiency thereof is maximized and a cost of manufacture, a weight, and an assembly time thereof are minimized. 
     SUMMARY OF THE INVENTION 
     Harmonious with the present invention, an oil separator wherein an oil separation efficiency thereof is maximized and a cost of manufacture, a weight, and an assembly time thereof are minimized has surprisingly been discovered. 
     In one embodiment, an oil separator for a compressor comprises: a drive shaft including a passageway formed therein, the passageway in communication with a suction chamber of the compressor; and a rotation imparting structure disposed on the drive shaft having a passageway formed therein, the passageway in communication with a crank chamber of the compressor and with the passageway formed in the drive shaft to provide fluid communication between the crank chamber of the compressor and the suction chamber of the compressor. 
     In another embodiment, a compressor comprises: a head including a suction chamber formed therein; a crank case including a crank chamber formed therein; a cylinder block disposed between the head and the crank case, the cylinder block having a plurality of pistons reciprocatingly disposed therein; a drive shaft rotatingly disposed in the crank chamber and having a passageway formed therein, the passageway in fluid communication with the suction chamber; and a rotation imparting structure disposed on the drive shaft and having a passageway formed therein, the passageway in fluid communication with the crank chamber and with the passageway formed in the drive shaft to provide fluid communication between the crank chamber and the suction chamber. 
     A method for separating oil from a second fluid in a compressor is disclosed, wherein the method comprises the steps of: providing a drive shaft adapted to be disposed in a crank chamber, the drive shaft having a first aperture formed on an outer surface thereof and a passageway formed in an inner portion thereof, the first aperture in fluid communication with the passageway; providing a rotation imparting structure adapted to be disposed on the drive shaft, the rotation imparting structure having a first aperture formed on an outer surface thereof and a passageway formed in an inner portion thereof, the passageway in fluid communication with the passageway formed in the drive shaft; causing a mixture of fluid to enter the rotation imparting structure; and causing the drive shaft and the rotation imparting structure to rotate about an axis of rotation to cause a separation of the mixture of fluid by a centrifugal force. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above, as well as other objects and advantages of the invention, will become readily apparent to those skilled in the art from reading the following detailed description of a preferred embodiment of the invention when considered in the light of the accompanying drawings in which: 
         FIG. 1  shows a sectional view of a variable displacement swash plate-type compressor illustrating a flow path in accordance with an embodiment of the invention; 
         FIG. 2  shows a perspective view of a drive shaft in accordance with another embodiment of the invention; 
         FIG. 3  shows a sectional view of a rotor illustrated in  FIG. 1  in accordance with another embodiment of the invention; and 
         FIG. 4  shows a sectional view of a swash ring and a drive shaft in accordance with another embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The following detailed description and appended drawings describe and illustrate various exemplary embodiments of the invention. The description and drawings serve to enable one skilled in the art to make and use the invention, and are not intended to limit the scope of the invention in any manner. In respect of the methods disclosed and illustrated, the steps presented are exemplary in nature, and thus, the order of the steps is not necessary or critical. 
       FIG. 1  shows a variable displacement swash plate-type compressor  10  in accordance with an embodiment of the invention. The compressor  10  includes a cylinder block  12  having a plurality of cylinders  14  formed therein. A head  16  is disposed adjacent one end of the cylinder block  12  and sealingly closes the end of the cylinder block  12 . A valve plate  18  is disposed between the cylinder block  12  and the head  16 . The head  16  includes a suction chamber  20  and a discharge chamber  22 . The suction chamber  20  communicates with the cylinders  14  through a suction port  24  formed in the valve plate  18 . The cylinders  14  communicate with the discharge chamber  22  through a discharge port  26  formed in the valve plate  18 . A crankcase  28  is sealingly disposed at the other end of the cylinder block  12 . The crankcase  28  and cylinder block  12  cooperate to form an airtight crank chamber  30 . 
     A drive shaft  32  having a first end  33  and a second end  35  is centrally disposed in and extends through the crankcase  28  to the cylinder block  12 . The drive shaft  32  is rotatably supported by a bearing  34  mounted in the crankcase  28  and a bearing  36  mounted in the cylinder block  12 . A radially outwardly extending passageway  39  and an axially outwardly extending passageway  41  are formed in the drive shaft  32 . It is understood that additional radially outwardly extending passageways (not shown) can be formed in the drive shaft  32  and connected to the axially outwardly extending passageway  41  as desired, such as an array of radially outwardly extending passageways, for example. The radially outwardly extending passageway  39  and the axially outwardly extending passageway  41  cooperate to form a fluid passageway from a radial outer surface  38  of the drive shaft  32  to the second end  35  of the drive shaft. 
     A fluid passageway  43  is formed in the cylinder block  12  and provides fluid communication between the fluid passageway formed in the drive shaft  32  and the suction port  24 . A seal  47  is sealingly engaged to the drive shaft  32  and a drive shaft support bore  49 . Such a seal is disclosed in U.S. Pat. No. 6,942,465, herein incorporated by reference in its entirety. 
     A rotor  40  is mounted within the crank chamber  30  on the drive shaft  32 . Rotor, as used herein, is meant to include rotation imparting structures such as a swash plate, a swash ring, a wobble plate, a thrust disc, an extension of the drive shaft, and the like, for example. The rotor  40  includes a fluid passageway  46  formed therein. It is understood that additional fluid passageways can be formed in the rotor  40  or additional rotors disposed on the drive shaft  32  as desired. The fluid passageway  46  extends from a centrally formed aperture  45  formed in the rotor  40  to a radial outer surface  44  of the rotor  40 . The fluid passageway  46  provides a flow path between the crank chamber  30  and the fluid passageway formed in the drive shaft  32 . The fluid passageways  46 ,  39 ,  41 ,  43  cooperate form a flow path between the crank chamber  30  and the suction chamber  20 . 
     A thrust bearing  48  is mounted in the crank chamber  30  on an inner wall  49  of the crankcase  28  and is disposed between the crankcase  28  and the rotor  40 . The thrust bearing  48  provides a bearing surface for the rotor  40 . An arm  50  extends laterally outwardly from a surface of the rotor  40  opposite the surface of the rotor  40  that contacts the thrust bearing  48 . A slot (not shown) is formed adjacent a distal end  51  of the arm  50 . A pin  52  has a first end (not shown) slidingly disposed in the slot of the arm  50  of the rotor  40 . 
     A swash plate assembly  53  includes a hub  54  and an annular plate  56 . As is known in the art, the hub  54  and annular plate  56  may be formed separately or as an integral piece. The hub  54  includes a hollow, cylindrical main body  58  having a central aperture  59  that receives the drive shaft  32 . The annular plate  56  has a pair of opposed, substantially flat surfaces  68  and a central aperture  70  formed therein. The main body  58  of the hub  54  is received in the aperture  70  of the annular plate  56  to form the swash plate assembly  53 . An arm  60  extends laterally and radially outwardly from the main body  58 . An aperture  64  that receives a second end (not shown) of the pin  52  is formed adjacent a distal end  62  of the arm  60 . 
     A coil spring  72  is disposed around the radial outer surface  38  of the drive shaft  32 . A first end  74  of the spring  72  abuts the rotor  40  and a spaced apart second end  76  of the spring  72  abuts the hub  54 . 
     A piston  82  is slidably disposed in each of the cylinders  14  in the cylinder block  12 . Each of the pistons  82  includes a head  84  and a skirt portion  86  that terminates in a bridge portion  88 . 
     A pair of concave shoe pockets  90  is formed in the bridge portion  88  of each piston  82  for receiving a pair of semi-spherical shoes  92 . 
     Operation of the compressor  10  is accomplished by rotation of the drive shaft  32  about an axis of rotation X-X. The rotation is caused by an auxiliary drive means (not shown) such as an internal combustion engine of a vehicle, for example. Rotation of the drive shaft  32  causes a corresponding rotation of the rotor  40 . The swash plate assembly  53  is connected to the rotor  40  by a hinge mechanism formed by the pin  52  slidingly disposed in the slot of the arm  50  of the rotor  40 , and fixedly disposed in the aperture  64  of the arm  60  of the hub  54 . As the rotor  40  rotates, the connection made by the pin  52  between the swash plate assembly  53  and the rotor  40  causes the swash plate assembly  53  to rotate. During rotation, the swash plate assembly  53  is disposed at an inclination angle, which may be adjusted as is known in the art. The inclination angle of the swash plate assembly  53 , the sliding engagement between the annular plate  56  and the shoes  92 , and the rotation of the shoes  92  in the pockets  90  of the bridge portion  88  of the pistons.  82 , causes a reciprocation of the pistons  82 . 
     As the pistons  82  reciprocate, the pressure inside the discharge chamber  22  is greater than the pressure inside the crank chamber  30 , which is greater than the pressure inside the suction chamber  20 . These pressure differences between the discharge chamber  22  the crank chamber  30 , and the suction chamber  20  cause a first fluid such as a refrigerant (not shown), for example, and a second fluid (not shown), such as oil, for example to flow into the crank chamber  30 , where the two fluids are mixed. The pressure difference between the crank chamber  30  and the suction chamber  20  causes the mixture to flow into the passageway  46  formed in the rotor  40 . The seal  47  militates against the flow of fluid directly from the crank chamber  30  into the suction chamber  20 . The rotation of the rotor  40  generates a centrifugal force that is exerted upon the mixture. The density of the oil is higher than the density of the refrigerant. The differences in material properties between the refrigerant and the oil and the centrifugal force exerted on the mixture causes a separation of the oil from the refrigerant. Since the oil has a higher density than the refrigerant, the oil is caused to remain in the crank chamber  30 , while the refrigerant flows through the passageways  46 ,  39 ,  41 ,  43  to the suction chamber  20 . 
     The amount of centrifugal force exerted on an object is proportional to the distance the object is disposed from the axis of rotation. Accordingly, since the centrifugal force is exerted on the mixture of refrigerant and oil at a larger distance from the axis of rotation X-X than if the mixture were disposed in the drive shaft  32 , the amount of centrifugal force exerted on the mixture is maximized. 
     Once the oil is separated from the refrigerant, additional centrifugal forces exerted upon the oil cause the oil to be distributed from the passageway  46  formed in the rotor  40  back into the crank chamber  30 . Accordingly, the amount of oil preserved in the crank chamber  30  of the compressor  10  and the efficiency of the compressor  10  are maximized. 
     It is understood that other types of compressors, such as a fixed displacement type compressor, for example, can incorporate the oil separation structure described above without departing from the scope and spirit of the invention. In a fixed displacement type compressor that includes a rotary valve, such as disclosed in U.S. Pat. No. 5,372,483, the drive shaft  32  may include a second radially outwardly extending passageway (not shown) formed therein. The second radially outwardly extending passageway is formed between the rotation imparting structure and the end of the drive shaft that includes the rotary valve. The oil separating features described above would be useful in this type of compressor, since the oil would be separated from the refrigerant in the radially outwardly extending passageway formed in the rotation imparting structure before the refrigerant would be introduced into a cylinder. 
       FIG. 2  shows a drive shaft  100  in accordance with an embodiment of the invention. A radial outer surface  102  of the drive shaft  100  includes a channel  104  formed therein. A fluid passageway  112  is formed in the drive shaft  100 . The fluid passageway  112  includes an axially outwardly extending passageway  108  that extends from a distal end  110  of the drive shaft  100  to a radially outwardly extending passageway  106  that extends from the axially outwardly extending passageway  108  to the channel  104 . It is understood that additional passageways (not shown) can be formed in the drive shaft  100  as desired, such as an annular array of passageways, for example. 
     A rotation imparting structure (not shown) such as a rotor or a thrust disc, for example, is mounted to the drive shaft  100  and surrounds the channel  104 . A fluid passageway formed in the rotation imparting structure is aligned with and in fluid communication with the channel  104  formed in the drive shaft  100 . 
     In use, the channel  104  formed in the drive shaft  100  facilitates fluid communication between the passageway formed in the rotation imparting structure and fluid passageway  112  formed in the drive shaft  100 . The fluid communication is facilitated without a direct angular alignment between the passageway formed in the rotation imparting structure and the radially outwardly extending passageway  106  formed in the drive shaft  100 . Use of the drive shaft  100  within the compressor is the same as discussed above for  FIG. 1 . 
       FIG. 3  shows the rotor  40 ′ described in  FIG. 1  in accordance with another embodiment of the invention. Similar structure to that described above for  FIG. 1  repeated herein with respect to  FIG. 3  includes the same reference numeral and a prime (′) symbol. The rotor  40 ′ includes a fluid passageway  46 ′ formed therein and is mounted on a drive shaft (not shown) in a compressor (not shown) that includes a discharge chamber (not shown), a crank chamber (not shown), and a suction chamber (not shown), as discussed in  FIG. 1 . A hollow tube  202  is disposed on a radial outer surface  44 ′ of the rotor  40 ′ adjacent the fluid passageway  46 ′. 
     A first end  204  of the hollow tube  202  is aligned with the fluid passageway  46 ′ formed in the rotor  40 ′ to provide a flow path between the hollow tube  202  and the passageway  46 ′ formed in the rotor  40 ′. A second end  206  of the hollow tube  202  is in fluid communication with the crank chamber. In the embodiment shown, an intermediate portion  208  of the hollow tube  202  includes a bend  210  formed therein. The bend  210  can be formed in any direction relative to the rotation of the rotor  40 ′ when in use. Favorable results have been found wherein the bend  201  is formed against the direction of rotation of the rotor  40 ′ when in use. 
     A porous material  212 , such as a filter, for example, is attached to the second end  206  of the hollow tube  202 . The porous material  212  shown is in the shape of a sphere. However, other shapes or configurations for the porous material  212  can be used as desired. 
     Pressure differences between the discharge chamber, the crank chamber, and the suction chamber cause a mixture of a first fluid such as a refrigerant (not shown), for example, and a second fluid such as oil (not shown), for example, to flow into the crank chamber as discussed above for  FIG. 1 . The pressure difference between the suction chamber and the crank chamber causes the mixture to flow into the hollow tube  202 . The rotation of the rotor  40 ′ generates a centrifugal force that is exerted upon the mixture. Differences in material properties between the refrigerant and the oil and the centrifugal force exerted on the mixture causes a separation of the oil from the refrigerant. Since the oil has a higher density than the refrigerant, the oil is caused to remain in the passageway  46 ′, while the refrigerant flows through the passageways formed in the rotor  40 ′ and the drive shaft and into to the suction chamber. 
     As discussed above, the amount of centrifugal force exerted on the mixture is maximized as a result of the larger distance of the mixture from an axis of rotation. 
     The hollow tube  202  provides a larger distance from the axis of rotation than the passageway  46 ′ formed in the rotor  40 ′. Accordingly, a separation of the oil from the refrigerant is maximized. 
     Once the oil is separated from the refrigerant, additional centrifugal forces exerted upon the oil cause the oil to be distributed from the passageway  46 ′ formed in the rotor  40 ′ back into the crank chamber. Accordingly, the amount of oil preserved in the crank chamber of the compressor is maximized, and the oil can be used to lubricate the internal components of the compressor, thus maximizing the efficiency of the compressor. 
     The bend  210  formed in the hollow tube  202  creates a more tortuous path for the mixture entering the hollow tube  202  from the crank chamber. Due to its higher density, the amount of oil permitted to flow into the hollow tube  202  is minimized. Accordingly, the amount of oil retained in the crank chamber is maximized. 
     The porous material  212  militates against the flow of oil into the hollow tube  202  by filtering the oil from the mixture. As the oil is filtered it is collected on the porous material  212 . Further, the porous material  212  militates against the flow of contaminates or other undesirable materials that may cause clogging into the hollow tube  202  and the rotor  40 ′. When the rotor  40 ′ rotates, centrifugal force is exerted on the oil and causes the oil to be detached from the porous material  212 . Accordingly, the oil is preserved in the crank chamber, thus maximizing an efficiency of the compressor. It is understood that the porous material  212  can be used without the hollow tube  202 , wherein the porous material  212  could be affixed directly to the rotor  40 ′ adjacent the passageway  46 ′. 
       FIG. 4  shows a swash ring assembly  300  for use in a compressor (not shown), such as a swash ring compressor, for example. In the embodiment shown, the swash ring assembly  300  is formed from bronze and is slidably and pivotally mounted on a drive shaft  302 . It is understood that the swash ring assembly  300  can be formed from other materials as desired. 
     The swash ring assembly  300  and the drive shaft  302  cooperate to house a pin  304 . In the embodiment shown, the pin  304  is formed from steel. It is understood that the pin  304  can be formed from other materials as desired. The pin  304  includes a main body portion  306  and a head portion  308 . In the embodiment shown, the head portion  308  is formed in the shape of a sphere. A pin having a similar shape is shown in PCT Pat. App. No. WO 2006/024345, herein incorporated by reference in its entity. However, it is understood that the head portion  308  can have other shapes as desired without departing from the scope and spirit of the invention. The pin  304  includes a fluid passageway  310  formed therein. The fluid passageway  310  includes an axially outwardly extending passageway  312  that extends from the head portion  308  into the main body portion  306 , and a radially outwardly extending passageway  314  that extends from the axially outwardly extending passageway  312  to a radial outer edge  316  of the pin  304 . The radially outwardly extending passageway  314  is substantially aligned with an axially outwardly extending passageway  317  formed in the drive shaft  302 , which is in fluid communication with a suction chamber (not shown) of the compressor. It is understood that additional pins (not shown) and/or fluid passageways can be formed in the swash ring assembly  300  as desired. 
     The head portion  308  of the pin is received by a housing  318  that is housed in the swash ring assembly  300 . The housing  318  is preferably formed from steel. It is understood that the housing  318  can be formed from other materials as desired. In the embodiment shown, an inner portion of the housing  318  substantially conforms to the geometry of the head portion  308  of the pin  304 . A first end  320  of the housing  318  includes an aperture  322  formed therein. The aperture  322  is substantially aligned with the axially outwardly extending passageway  312  formed in the pin  304 . 
     Operation of the compressor is accomplished by rotation of the drive shaft  302  about an axis of rotation X-X. The rotation is caused by an auxiliary drive means (not shown) such as an internal combustion engine of a vehicle, for example. Rotation of the drive shaft  302  causes a corresponding rotation of the swash ring assembly  300 . During rotation, the swash ring assembly  300  is disposed at an inclination angle, which may be adjusted as is known in the art. As the inclination angle of the swash ring assembly  300  is adjusted, the head portion  308  of the pin  304  pivots inside the housing  320 . Accordingly, alignment between the radially outwardly extending passageway  314  formed in the pin  304  and the axially outwardly extending passageway  317  formed in the drive shaft  302  is maintained. 
     The inclination angle of the swash ring assembly  300  causes a reciprocation of a plurality of pistons (not shown). As the pistons reciprocate, pressure differences between a discharge chamber (not shown), a crank chamber (not shown), and the suction chamber cause a first fluid such as a refrigerant (not shown), for example, and a second fluid (not shown), such as oil, for example, to flow into the crank chamber, where the two fluids are mixed. As discussed above for  FIG. 1 , the pressure difference between the crank chamber and the suction chamber causes the mixture to flow into the passageway  310  formed in the pin  304 . The rotation of the rotor swash ring assembly  300  generates a centrifugal force that is exerted upon the mixture. Differences in material properties between the refrigerant and the oil and the centrifugal force exerted on the mixture causes a separation of the oil from the refrigerant. Since the oil has a higher density than the refrigerant, the oil is caused to remain in the passageway  310 , while the refrigerant flows through the passageways  312 ,  314 ,  317  to the suction chamber. 
     As discussed above for  FIG. 1 , the amount of centrifugal force exerted on an object is proportional to the distance the object is disposed from the axis of rotation. Accordingly, since the centrifugal force is exerted on the mixture of refrigerant and oil at a larger distance from the axis of rotation X-X than if the mixture were disposed in the drive shaft  302 , the amount of centrifugal force exerted on the mixture is maximized. 
     Once the oil is separated from the refrigerant, additional centrifugal forces exerted upon the oil causes the oil to be distributed from the passageway  310  formed in the pin  304  back into the crank chamber. Accordingly, the amount of oil preserved in the crank chamber of the compressor and the efficiency of the compressor are maximized. 
     It is understood that other types of compressors, such as a fixed displacement type compressor, for example, can incorporate the oil separation structure described above without departing from the scope and spirit of the invention. 
     From the foregoing description, one ordinarily skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications to the invention to adapt it to various usages and conditions.