Patent Publication Number: US-2019195122-A1

Title: Turbocharger having variable compressor trim

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention generally relates to a compressor for use in a turbocharger of a vehicle. 
     2. Description of the Related Art 
     Turbochargers receive exhaust gas from an internal combustion engine and deliver compressed air to the internal combustion engine. Turbochargers are used to increase power output of the internal combustion engine, lower fuel consumption of the internal combustion engine, and reduce emissions produced by the internal combustion engine. Delivery of compressed air to the internal combustion engine by the turbocharger allows the internal combustion engine to be smaller, yet able to develop the same or similar amount of horsepower as larger, naturally-aspirated internal combustion engines. Having a smaller internal combustion engine for use in a vehicle reduces the mass and aerodynamic frontal area of the vehicle, which helps reduce fuel consumption of the internal combustion engine and improve fuel economy of the vehicle. 
     Typical turbochargers include a turbine housing defining a turbine housing interior, a turbine wheel disposed within the turbine housing interior, and a shaft coupled to and rotatable by the turbine wheel. Typical turbochargers also include a compressor housing defining a compressor housing interior and a flow path. The flow path fluidly couples the interior of the compressor housing with the internal combustion engine. Typical turbochargers further include a compressor wheel disposed within the interior of the compressor housing and coupled to the shaft. The compressor wheel is rotatable by the shaft for delivering the compressed air to the internal combustion engine through the flow path. Specifically, energy from exhaust gas from the internal combustion engine, which would normally be wasted energy, is used to drive the turbine wheel, which is used to drive the shaft and, in turn, the compressor wheel to the deliver compressed air to the internal combustion engine. 
     The compressor has a trim which influences the amount of airflow through the compressor wheel. As such, depending on the desired performance of the internal combustion engine, typical compressor wheels are designed to deliver a target airflow to the internal combustion engine. In typical turbochargers, the airflow through the compressor wheel and to the internal combustion engine may also be influenced by other factors. 
     Typical compressors in single stage turbochargers have a constant trim which limits airflow through the compressor wheel to a constant flow. However, more recent compressors may include a variable compressor trim. Known variable compressor trims include overlapping single-layer vanes which can lead to undesirable leakage of air into the compressor housing. 
     As such, there remains a need to provide for an improved variable compressor trim for use in a turbocharger. 
     SUMMARY OF THE INVENTION AND ADVANTAGES 
     A turbocharger for receiving exhaust gas from an internal combustion engine and for delivering compressed air to the internal combustion engine includes a turbine housing which defines a turbine housing interior. The turbocharger also includes a turbine wheel disposed within the turbine housing interior for receiving the exhaust gas from the internal combustion engine. A turbocharger shaft is coupled to and rotatable by the turbine wheel, and the turbocharger shaft extends along an axis that extends longitudinally through the turbine housing interior. Moreover, the turbocharger includes a compressor housing defining an interior, with the compressor housing having an air inlet portion spaced from the turbocharger shaft and disposed about the axis, and the air inlet defines an inlet diameter (ID) perpendicular to the axis. 
     The turbocharger also includes a compressor wheel disposed within the interior of the compressor housing and coupled to the turbocharger shaft. The compressor wheel is rotatable by the turbocharger shaft and is disposed between the air inlet portion and the turbine wheel for delivering compressed air to the internal combustion engine. Finally, the turbocharger includes an airflow adjustment assembly. 
     The airflow adjustment assembly includes a plurality of guide vanes at least partially disposed within the interior of the compressor housing. Each of the plurality of guide vanes has a guide tip and a guide base spaced from the guide tip along the axis. Moreover, each of the guide bases are pivotably coupled to the air inlet portion. The guide tips define a vane diameter (VD) less than the inlet diameter (ID) and perpendicular to the axis. The airflow adjustment assembly further includes a sliding ring at least partially disposed within the interior, and a plurality of connecting rods at least partially disposed within the interior. The sliding ring is configured to be axially movable along the axis. Each of the connecting rods are disposed between and coupled to one of the guide vanes at the guide base and the sliding ring. 
     Additionally, the plurality of connecting rods are axially moveable along the axis when the sliding ring moves axially along the axis, thereby selectively increasing and/or decreasing the vane diameter (VD) when the sliding ring moves axially along the axis. 
     Accordingly, the plurality of guide vanes allow the compressor trim to be adjusted when desired. The compressor trim is defined as the outlet diameter of the airflow adjustment assembly, which is also known as the vane diameter. Adjusting the compressor trim or vane diameter allows the turbocharger to achieve higher pressure ratios at low engine speeds by changing the diameter of the compressor trim. This allows a single stage compressor to perform at a similar performance and efficiency of a multiple stage compressor while implementing the space saving advantage of the single stage compressor. Moreover, providing a support ring coupled to the airflow adjustment assembly allows ease of installation and repair inside the compressor housing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other advantages of the present invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein: 
         FIG. 1  is a schematic partial cross-section illustration of a turbocharger; 
         FIG. 2  is perspective view of a compressor removed from the turbocharger; 
         FIG. 3  is a perspective view of an airflow adjustment assembly removed from the compressor; 
         FIG. 4  is a perspective view of a guide vane of the airflow adjustment assembly; 
         FIG. 5  is a bottom plan view of the guide vane of the airflow adjustment assembly; 
         FIG. 6  is a side view of the guide vane of the airflow adjustment assembly; 
         FIG. 7  is a top plan view of the guide vane of the airflow adjustment assembly; 
         FIG. 8  is cross-sectional view of the compressor including a compressor housing and a sliding ring in a first position; 
         FIG. 9  is a cross-sectional view of the compressor including the compressor housing and the sliding ring in a second position; 
         FIG. 10  is a schematic partial cross-section illustration of a turbocharger according to another embodiment; 
         FIG. 11  is perspective view of a compressor removed from the turbocharger according to the embodiment illustrated in  FIG. 10 ; 
         FIG. 12A  is a perspective view of an airflow adjustment assembly removed from the compressor; 
         FIG. 12B  is an opposite perspective view of the airflow adjustment assembly removed from the compressor according to the embodiment illustrated in  FIG. 10 ; 
         FIG. 13  is a perspective view of a portion of the airflow adjustment assembly including a yoke and a cross-shaft according to the embodiment illustrated in  FIG. 10 ; 
         FIG. 14  is a side perspective view of the yoke and cross-shaft according to the embodiment illustrated in  FIG. 10 ; 
         FIG. 15  is a perspective view of a guide vane of the airflow adjustment assembly according to the embodiment illustrated in  FIG. 10 ; 
         FIG. 16  is a bottom plan view of the guide vane of the airflow adjustment assembly according to the embodiment illustrated in  FIG. 10 ; 
         FIG. 17  is a side view of the guide vane of the airflow adjustment assembly according to the embodiment illustrated in  FIG. 10 ; 
         FIG. 18  is a top plan view of the guide vane of the airflow adjustment assembly according to the embodiment illustrated in  FIG. 10 ; 
         FIG. 19  is cross-sectional view of the compressor including a compressor housing and a sliding ring in a first position according to the embodiment illustrated in  FIG. 10 ; and 
         FIG. 20  is a cross-sectional view of the compressor including the compressor housing and the sliding ring in a second position according to the embodiment illustrated in  FIG. 10 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to the embodiment illustrated in  FIGS. 1-9 , wherein like numerals indicate like parts throughout the several views, a turbocharger  20  is generally shown in  FIG. 1 . The turbocharger  20  receives exhaust gas from an internal combustion engine and delivers compressed air to the internal combustion engine. The turbocharger  20  includes a turbine housing  22  defining a turbine housing interior  24 . The turbine housing  22  receives and directs exhaust gas from the internal combustion engine. The turbocharger  20  includes a turbine wheel  26  within the turbine housing interior  24  for receiving the exhaust gas from the internal combustion engine. Specifically, the exhaust gas from the internal combustion engine is used to drive the turbine wheel  26 . The turbocharger  20  includes a shaft  28  coupled to and rotatable by the turbine wheel  26 . Specifically, the turbine wheel  26  is driven by the exhaust gas from the internal combustion engine, which, in turn, rotates the shaft  28 . The shaft  28  extends along an axis  38  that extends longitudinally through the turbine housing interior  24 . 
     The turbocharger  20  includes a compressor housing  30  defining an interior  32  of the compressor housing  30  and a flow path  34 . The interior  32  of the compressor housing  30  receives and directs air to the internal combustion engine. The flow path  34  fluidly couples the interior  32  of the compressor housing  30  with the internal combustion engine. The compressor housing  30  includes an air inlet portion  35  which is spaced apart from the shaft  28  and is disposed about the axis  38 . The air inlet defines an inlet diameter (ID) which is disposed perpendicular to the axis  38 . The turbocharger  20  includes a compressor wheel  36  disposed within the interior  32  of the compressor housing  30  and coupled to the shaft  28 . The compressor wheel  36  is disposed between the air inlet portion  35  and the turbine wheel  26 . The compressor wheel  36  is rotatable by the shaft  28  for delivering the compressed air to the internal combustion engine through the flow path  34 . 
     Referring now to  FIGS. 2 and 3 , the turbocharger  20  also includes an airflow adjustment assembly  40 . The airflow adjustment assembly  40  may be disposed at least partially within the interior  32  of the compressor housing  30 . It is also contemplated that certain components of the airflow adjustment assembly  40  may be disposed outside of the compressor housing  30 . In the embodiment illustrated in  FIG. 2 , the entire airflow adjustment assembly  40  is disposed within the interior  32  of the compressor housing  30 . Moreover, the flow path  34  is disposed parallel with the axis  38  and flows into the airflow adjustment assembly  40  at one end, flows through the airflow adjustment assembly  40  and exits the airflow adjustment assembly  40  at an opposite end where the air continues to flow into the compressor housing  30  towards the internal combustion engine. 
     The airflow adjustment assembly  40  includes a sliding ring  42  which is at least partially disposed within the interior  32  of the compressor housing  30 . The sliding ring  42  may be comprised of aluminum, steel, a plastic polymer or other material as known by one of ordinary skill in the art. The sliding ring  42  is configured to be axially movable between a first position  44  where air is not restricted from flowing though the interior  32  of the compressor housing  30 , and a second position  46  where air is at least partially restricted from flowing through the interior  32  of the compressor housing  30  along the axis  38 . As illustrated in the embodiment shown in  FIGS. 8 and 9 , when the sliding ring  42  is moved towards the first position  44 , the sliding ring  42  moves along the axis  38  in the opposite direction of the flow path  34 . Moreover, when the sliding ring  42  is moved towards the second position  46 , the sliding ring  42  moves along the axis  38  in the same direction as the flow path  34 . 
     Referring again to  FIGS. 2 and 3 , the sliding ring  42  has a generally circular, ring-like shape having an aperture in the center. The flow path  34  is configured to be disposed through the aperture of the sliding ring  42 . In the embodiment illustrated in  FIGS. 2 and 3 , the sliding ring  42  has a generally flat first surface and second surface which are connected by a curved outer and inner surface forming the ring shape. As shown in  FIGS. 2 and 3 , the top surface, bottom surface, inner surface, and outer surface generally have a similar width. However, it is contemplated that the widths of any of the surfaces may be larger or smaller than any other surface width of the sliding ring  42 . In the embodiment shown in  FIG. 3 , the sliding ring  42  is disposed perpendicular to the axis  38  such that the axis  38  is disposed through the aperture in the center of the sliding ring  42 . However, it is contemplated that the sliding ring  42  may be various other shapes and/or orientations configured to be axially moveable along the axis  38 . 
     Referring again to the embodiment illustrated in  FIG. 3 , the sliding ring  42  may include at least one, and as illustrated in  FIG. 3 , a plurality of connecting prongs  48  which extend from the second surface of the sliding ring  42 . As such, it is contemplated that the connecting prongs  48  may be made of the same material as the sliding ring  42  or may be made of a different material including but not limited to steel, aluminum, or a plastic polymer as known by one of ordinary skill in the art. In the embodiment shown in  FIG. 3 , the connecting prongs  48  extend the entire width of the bottom surface, however, various configurations have been contemplated. The connecting prongs  48  illustrated in  FIG. 3  are disposed in pairs about the bottom surface of the sliding ring  42 , having a space between each pair. A connecting rod  50  is configured to be disposed in the space between each pair of connecting prongs  48 . It is contemplated that a fastener is disposed through the pair of connecting prongs  48  and through the connecting rod  50  to secure the connecting rod  50  to the sliding ring  42 . However, it is also contemplated that the connecting rod  50  and the sliding ring  42  may be coupled in various other ways, as known by one of ordinary skill in the art. In the embodiment illustrated in  FIG. 3 , the sliding ring  42  includes four pairs of connecting prongs  48  corresponding to four connecting rods  50 ; however, any number of connecting prongs  48  and/or connecting rods  50  may be implemented in the airflow adjustment assembly  40 . 
     The connecting rods  50  are at least partially disposed within the interior  32  of the compressor housing  30  and are configured to move in the direction opposite the flow path  34  when the sliding ring  42  is moved to the first position  44  and move in the same direction as the flow path  34  when the sliding ring  42  is moved to the second position  46 . More specifically, the connecting rods  50  are axially movable along the axis  38  when the sliding ring  42  moves axially along the axis  38 . As illustrated in the embodiment shown in  FIG. 3 , the connecting rods  50  have a generally bar-shaped main section having a circular connecting portion on each end. The circular portions are configured to allow the fastener to couple a first circular portion to the connecting prongs  48  of the sliding ring  42 . On the opposite end of the connecting rod  50  is another circular portion which may be similar or identical to the first circular portion and is configured to pivotally couple the connecting rod  50  to a guide vane  52 . Again, a fastener may be disposed through the circular portion to secure the connecting rod  50  and the guide vane  52 . The connecting rods  50  may be comprised of steel, aluminum, or another material having sufficient strength to couple the sliding ring  42  to the guide vane  52  of the air flow adjustment assembly. 
     As illustrated in the embodiments shown in  FIG. 3 , the connecting rods  50  extend from the sliding ring  42  to the guide vane  52  and are configured to define a space between the sliding ring  42  and the guide vanes  52 . In the embodiment illustrated in  FIG. 3 , the airflow adjustment assembly  40  includes four connecting rods  50 , however it is contemplated that more or fewer connecting rods  50  may be disposed between the sliding ring  42  and the guide vanes  52 . As additionally illustrated in the embodiment shown in  FIG. 3 , a single connecting rod  50  is coupled to each guide vane  52 . However, it is additionally contemplated that multiple connecting rods  50  may be coupled to each guide vane  52  as desired by one of ordinary skill in the art. 
     Referring again to the embodiment shown in  FIG. 3 , the connecting rods  50  are coupled to the guide vanes  52  at a connecting protrusion  54  of the guide vane  52 . As illustrated in  FIG. 3 , the connecting protrusion  54  is comprised of a pair of protrusions configured to have the connecting rod  50  disposed between the pair of protrusions. The fastener is then disposed through each protrusion and the circular portion of the connecting rod  50  to pivotally couple the guide vane  52  to the connecting rod  50 . Various other configurations have also been contemplated which allow the connecting rod  50  and the guide vane  52  to be pivotally coupled to one another without departing from the spirit of the invention. Moreover, it is contemplated that the sliding ring  42  and the guide vane  52  may be coupled to one another using another mechanism without departing from the spirit of the invention. 
     The sliding ring  42  is additionally coupled to a cradle  56  which is at least partially disposed with the interior  32  of the compressor housing  30 . As illustrated in  FIGS. 2 and 3 , the cradle  56  may have a generally semi-circle shape and is disposed in the direction opposite the direction of airflow from the sliding ring  42 . The cradle  56  is pivotally coupled to the sliding ring  42  and configured to move the sliding ring  42  axially along the axis  38  between the first position  44  and the second position  46 . It is contemplated that the cradle  56  may be a variety of other shapes or configurations configured to be pivotally coupled to the sliding ring  42  as known by one of ordinary skill in the art. The cradle  56  is typically comprised of the same material as the sliding ring  42  such as steel, aluminum or aluminum alloy, or a plastic polymer. However, the cradle  56  may be comprised of any other material as desired by one of ordinary skill in the art. 
     As shown in the embodiment illustrated in  FIG. 3 , the cradle  56  has a coupler  58  disposed on each distal end of an inside surface of the cradle  56 . Each of the couplers  58  are configured to engage a connecting pin  60  which pivotally couples the sliding ring  42  and the cradle  56 . It is contemplated that the coupler  58  is configured to allow the cradle  56  to tilt in a direction opposite the direction of the flow path  34  to move the sliding ring  42  from the first position  44  to the second position  46 . More specifically, a top portion of the cradle  56  which is disposed along the semi-circle between the two distal ends of the cradle, is configured to move in the direction opposite the direction of the flow path  34  while the ends of the cradle  56  move in the direction of the flow path  34  to move the connecting pins  60  which move the sliding ring  42  from the first position  44  to the second position  46 . 
     Referring again to the embodiment illustrated in  FIG. 3 , the cradle  56  is coupled to the sliding ring  42  using the connecting pins  60  and the couplers  58 . It is contemplated that two connecting pins  60  may couple the sliding ring  42  and the cradle  56  as illustrated in  FIG. 3 ; however, more or less connecting pins  60  may be used as desired by one of ordinary skill in the art. As also illustrated in  FIG. 3 , the connecting pins  60  may be coupled to the sliding ring  42  through guide bushings. However, it is contemplated that the connecting pins  60  may be coupled to the sliding ring  42  using another method as known by one of ordinary skill in the art. It is also contemplated that the cradle  56  is coupled to the sliding ring  42  using another connection method other than the coupler  58 /connecting pin  60  mechanism as described above, as known by one of ordinary skill in the art. 
     As illustrated in the embodiment shown in  FIG. 3 , the cradle  56  may include a rectangular tab  62  disposed approximately equidistant between the two distal ends of the cradle  56  along the semi-circle. The rectangular tab  62  is configured to engage a cross-shaft  64 . The cross-shaft  64  may be composed of steel, aluminum or aluminum alloy, a plastic polymer, or any other material as known by one of ordinary skill in the art. As illustrated in the embodiment shown in  FIG. 3 , the cross-shaft  64  is disposed perpendicular to the axis  38  and is fixed to the rectangular tab  62  of the cradle  56 . As additionally illustrated in the embodiment shown in  FIG. 3 , the cross-shaft  64  is typically a cylindrical rod having two ends. However, it is contemplated that the cross-shaft  64  may be rectangular, triangular, or any other shape as desired by one of ordinary skill in the art. It is also contemplated that, as illustrated in  FIG. 3 , the cylindrical rod portion of the cross-shaft  64  may have an indented portion  70 . The indented portion  70  may extend around the entire circumference of the cross-shaft  64  or may only extend around a portion of the circumference of the cross-shaft  64 , as illustrated in  FIG. 3 . The cradle  56  may also be attached to the cross shaft  64  by having a through hole disposed in the cradle  56  which is configured to allow the cross-shaft  64  to pass directly through the cradle  56 . Additionally, it is contemplated that the cross shaft  64  and the cradle  56  may be coupled using a clamp, an interference fit, or another connection method as known by one of ordinary skill in the art. Each end of the cross-shaft  64  may include a bushing  66  as illustrated in  FIG. 3 , or may include another connection feature allowing the cross-shaft  64  to be coupled to another device. 
     In the embodiment illustrated in  FIG. 3 , one end of the cross-shaft  64  includes an actuation gear  68 . The actuation gear  68  is configured to be actuated by a gear assembly or other mechanism. When actuated, the actuation gear  68  is configured to rotate which in turn pulls the rectangular tab  62  of the cradle  56  such that the cradle  56  tilts and in turn moves the sliding ring  42  axially along the axis  38  from the first position  44  to the second position  46 . The actuation gear  68  is typically comprised of steel, however the actuation gear  68  may be comprised of another material which has the strength required to rotate the cross-shaft  64 , as known by one of ordinary skill in the art. As illustrated in the embodiment shown in  FIG. 3 , the actuation gear  68  has a rounded bottom portion which fans-out towards an upper portion which includes gear fingers for engaging another mechanism for actuation of the cross-shaft  64 . However, it is contemplated that the actuation gear  68  may be any other shape or configuration as desired by one of ordinary skill in the art, including but not limited to a control lever which may be actuated by a pneumatic actuator or vacuum actuator or other actuator has known by one of ordinary skill in the art. 
     Referring now to the embodiment shown in  FIGS. 4-7 , the guide vanes  52  are at least partially disposed within the interior  32  of the compressor housing  30 . The guide vanes  52  are generally comprised of steel, aluminum or aluminum alloy, a plastic polymer, or another material as known by one of ordinary skill in the art. Additionally, the guide vanes  52  have a separate outer surface  72  and an inner surface  74 . However, it is also contemplated that the guide vanes  52  may be comprised of a single piece without departing from the spirit of the invention. It is contemplated that the outer surface  72  and inner surface  74  may be comprised of the same material or the outer surface  72  and the inner surface  74  may be comprised of different materials from one another. Both the outer surface  72  and the inner surface  74  of each guide vane  52  are configured to form a seal between each of the guide vanes  52  when the sliding ring  42  is in the first position  44  and when the sliding ring  42  is in the second position  46 . 
     As illustrated in the embodiment shown in  FIGS. 4-7 , each guide vane  52  may be disposed within the interior  32  of the compressor housing  30 . In the embodiment illustrated in the figures, the guide vanes  52  are curved slightly and disposed adjacent to one another, forming a guide drum  76 . More specifically, the guide vanes  52  are curved such that the guide vanes  52  are disposed circumferentially about the axis  38  such that the guide vanes  52  form a circle having the axis  38  disposed through the center. In the embodiment illustrated in  FIG. 3 , four guide vanes  52  are disposed about the axis  38  forming the guide drum  76 . However, it is contemplated that more or less guide vanes  52  may comprise the guide drum  76 . Further, the inner surface  74   s  of the guide vanes  52  define an interior of the guide drum  76  which the flow path  34  flows through. Additionally, each of the guide vanes  52  have a guide tip  80  and a guide base  78 , where each of the guide bases  78  are pivotally coupled to the air inlet portion  35 . The guide base  78  is spaced from the guide tip  80  along the axis  38 . The guide tips  80  of the guide vanes  52  define a vane diameter (VD). The vane diameter (VD) is measured from the inner surface  74  of one guide vane  52  to the inner surface  74  of an opposite guide vane  52  and is disposed perpendicular to the axis  38 . Moreover, the vane diameter (VD) is less than the inlet diameter (ID). Additionally, the vane diameter (VD) is configured to be increased when the sliding ring  42  is moved to the first position  44  and to be decreased when the sliding ring  42  is moved to the second position  46 . 
     Referring again to the embodiment illustrated in  FIGS. 4-7 , the inner surface  74  and outer surface  72  are separate surfaces and are disposed against each other, i.e. a top surface of the inner surface  74  is disposed against the bottom surface of the outer surface  72 . Each of the inner surface  74  and the outer surface  72  have four sides. The first side, the second side, and the third side form three sides of a rectangle such that the first side and the second side are disposed parallel to one another and the third side is disposed at approximately a 90 degree angle to both the first and second side. The fourth side connects the first side and the second side, however, the fourth side is angled such that the first side has a length that is longer than the second side. Additionally, the first side includes may include an indent  82 , as illustrated in  FIGS. 4-7 , which is configured to allow the connecting rod  50  to be disposed between the pair of connecting prongs  48  and coupled to the guide base  78 . It is also contemplated that the guide base  78  may not include an indent  82  such that the connecting rod  50  is coupled to the guide vane  52  using another configuration. 
     As illustrated best in  FIGS. 4, 5, and 7  the outer surface  72  and the inner surface  74  are arranged offset from one another such that the angled or fourth side of the outer surface  72  is matched up with the first side, or side parallel to the axis  38 , of the inner surface  74 . In other words, a portion of the inner surface  74  is visible from a top view, as illustrated in  FIG. 7 , and a portion of the outer surface  72  is visible when viewed from a bottom view, as illustrated in  FIG. 6 . This configuration allows the guide drum  76  to have an air-tight seal between guide vanes  52  when the sliding ring  42  is in the first position  44  and when the sliding ring  42  is in the second position  46 . Additionally, this configuration may also provide an air tight seal between the guide vanes  52  when the sliding ring  42  is being moved from the first position  44  to the second position  46  and when the sliding ring  42  is being moved from the second position  46  to the first position  44 . It is additionally contemplated that various other configurations of the guide vanes  52  may be implemented which provide an air-tight seal of the guide drum  76 . 
     As best illustrated in  FIGS. 4 and 6 , the connecting protrusions  54  of the guide vane  52  are coupled to either the inner surface  74  or the outer surface  72  of the guide vane  52 . However, it is also contemplated that the connecting protrusions  54  of the guide vane  52  are coupled to both the inner surface  74  and the outer surface  72  of the guide vane  52 . As the connecting protrusions  54  are coupled to the connecting rods  50  and the sliding ring  42 , the connecting protrusions  54  are configured to move both the inner surface  74  and the outer surface  72  of guide vane  52  as one piece when the sliding ring  42  is moved between the first position  44  and the second position  46 . It is also contemplated that the inner surface  74  and the outer surface  72  could be moved separately if desired by one of ordinary skill in the art. Referring again to the embodiment illustrated in  FIGS. 4 and 6 , the inner surface  74  has a length which is longer than a length of the outer surface  72  such that the connecting prongs  48  are partially disposed on the inner surface  74  exclusively before also coupling the outer surface  72 . It is additionally contemplated that various other configurations of the guide vane  52  and connecting prongs  48  may be implemented without departing from the spirit of the invention which allow the inner surface  74  and the outer surface  72  of the guide vanes  52  to be coupled to the connecting rods  50 . 
     Referring now to the embodiment shown in  FIGS. 8 and 9 , in operation, the sliding ring  42  begins in the first position  44  shown in  FIG. 8 . When the sliding ring  42  is in the first position  44 , the cradle  56  is disposed perpendicular to the axis  38  while the actuation gear  68  of the cross-shaft  64  is not actuated, as illustrated in  FIG. 8 . However, it is also contemplated that when the sliding ring  42  is in the first position  44 , the cradle  56  may be disposed at an angle which is negative or positive relative to the axis. Additionally, when the sliding ring  42  is in the first position  44 , the vane diameter (VD) is at its largest such that the air flow is not restricted in the flow path  34  through the airflow adjustment device. As illustrated in  FIG. 8 , the vane diameter (VD) is at its largest when the guide vanes  52  extend parallel to axis  38 , however, it is also contemplated that the largest diameter may occur when the guide vanes  52  extend at an angle either above parallel to the axis  38 . When desired, the actuation gear  68  may be activated by any mechanism as known by one of ordinary skill in the art. When the actuation gear  68  is activated, the cross-shaft  64  rotates which moves the cradle  56 . The cradle  56  is moved or tilted to an angle which may be positive or negative relative to the axis  38 . The angle may be a slight angle such as between 5 and 15 degrees or may be a bigger angle such as between 5 and 45 degrees. It is additionally contemplated that the cradle  56  may be rotated up to 90 degrees as desired by one of ordinary skill in the art. Moreover, it is also contemplated that any of the angles described may be negative angles with respect to the position of the cradle  56  when the sliding ring  42  is in the first position  44 . When the cradle  56  is moved, the connecting pins  60  push the sliding ring  42  in a direction of the flow path  34  along the axis  38  and into the second position  46 . In the second position  46 , the sliding ring  42  engages the connecting rods  50  which allow the guide vanes  52  to pivot towards the center of the guide drum  76  such that the vane diameter (VD) is decreased. As illustrated in  FIG. 9 , when the sliding ring  42  is in the second position  46  the vane diameter (VD) is decreased from when the sliding ring  42  is in the first position  44  such that the air is at least partially restricted from flowing through the interior  32  of the compressor along the flow path  34 . When the sliding ring  42  is in the first position  44  and when the sliding ring  42  is in the second position  46 , the guide vanes  52  are sealed to one another such that no air escapes between the guide vanes  52  and all of the air entering the airflow adjustment assembly  40  moves through the airflow adjustment assembly  40  and exits the airflow adjustment assembly  40  to the compressor housing  30 . 
     It is also contemplated that, when desired, the sliding ring  42  can be moved from the second position  46  to the first position  44 . To achieve this, the actuation gear  68  of the cross-shaft  64  may be engaged by a mechanism which rotates the cross-shaft  64  to the position illustrated in  FIG. 8 . The cradle  56  is then moved to be perpendicular to the axis  38 . The connecting pins  60  pull the sliding ring  42  to the first position  44 . When the sliding ring  42  is moved to the first position  44 , the connecting rods  50  are engaged and pivot the guide vanes  52  away from the center of the guide drum  76  until the vane diameter (VD) is at its largest. Moreover, it is contemplated that the vane diameter (VD) may be held in any position between the position corresponding with the first position  44  of the sliding ring  42  and the position corresponding with the second position  46  of the sliding ring  42 . 
     One advantage of controlling the vane diameter (VD) is to achieve higher pressure ratios at a low engine speed. This improves the map width of a single compressor and increases the surge line of the compressor which allows better operating efficiency of the compressor and better intake throttling. By controlling the vane diameter (VD) in a single stage compressor by the method and apparatus described above, a similar performance of a multiple stage compressor may be achieved with the space saving advantages that come with a single stage compressor. The apparatus and method as described above also allow the turbocharger to achiever higher Exhaust Gas Recirculation (EGR) rates without impacting power rating. Additionally, the apparatus as described above may increase Low End Torque (LET) which would allow engine downsizing. 
     With reference now to the embodiment illustrated in  FIGS. 10-20 , wherein like numerals indicate like parts throughout the several views, another embodiment of turbocharger  20  is generally shown in  FIGS. 10 . The turbocharger  20  receives exhaust gas from an internal combustion engine and delivers compressed air to the internal combustion engine. The turbocharger  20  includes a turbine housing  22  defining a turbine housing interior  24 . The turbine housing  22  receives and directs exhaust gas from the internal combustion engine. The turbocharger  20  includes a turbine wheel  26  within the turbine housing interior  24  for receiving the exhaust gas from the internal combustion engine. Specifically, the exhaust gas from the internal combustion engine is used to drive the turbine wheel  26 . The turbocharger  20  includes a shaft  28  coupled to and rotatable by the turbine wheel  26 . Specifically, the turbine wheel  26  is driven by the exhaust gas from the internal combustion engine, which, in turn, rotates the shaft  28 . The shaft  28  extends along an axis  38  that extends longitudinally through the turbine housing interior  24 . 
     The turbocharger  20  includes a compressor housing  30  defining an interior  32  of the compressor housing  30  and a flow path  34 . The interior  32  of the compressor housing  30  receives and directs air to the internal combustion engine. The flow path  34  fluidly couples the interior  32  of the compressor housing  30  with the internal combustion engine. The compressor housing  30  includes an air inlet portion  35  which is spaced apart from the shaft  28  and is disposed about the axis  38 . The air inlet defines an inlet diameter (ID) which is disposed perpendicular to the axis  38 . The turbocharger  20  includes a compressor wheel  36  disposed within the interior  32  of the compressor housing  30  and coupled to the shaft  28 . The compressor wheel  36  is disposed between the air inlet portion  35  and the turbine wheel  26 . The compressor wheel  36  is rotatable by the shaft  28  for delivering the compressed air to the internal combustion engine through the flow path  34 . 
     Referring now to  FIGS. 11 and 12A -B, the turbocharger  20  also includes an airflow adjustment assembly  40 . The airflow adjustment assembly  40  may be disposed at least partially within the interior  32  of the compressor housing  30 . It is also contemplated that certain components of the airflow adjustment assembly  40  may be disposed outside of the compressor housing  30 . In the embodiment illustrated in  FIG. 11 , the entire airflow adjustment assembly  40  is disposed within the interior  32  of the compressor housing  30 . Moreover, the flow path  34  is disposed parallel with the axis  38  and flows into the airflow adjustment assembly  40  at one end, flows through the airflow adjustment assembly  40  and exits the airflow adjustment assembly  40  at an opposite end where the air continues to flow into the compressor housing  30  towards the internal combustion engine. 
     The airflow adjustment assembly  40  includes a sliding ring  42  which is at least partially disposed within the interior  32  of the compressor housing  30 . The sliding ring  42  may be comprised of aluminum, steel, a plastic polymer or other material as known by one of ordinary skill in the art. The sliding ring  42  is configured to be axially movable between a first position  44  where air is not restricted from flowing though the interior  32  of the compressor housing  30 , and a second position  46  where air is at least partially restricted from flowing through the interior  32  of the compressor housing  30  along the axis  38 . As illustrated in the embodiment shown in  FIGS. 19 and 20 , when the sliding ring  42  is moved towards the first position  44 , the sliding ring  42  moves along the axis  38  in the opposite direction of the flow path  34 . Moreover, when the sliding ring  42  is moved towards the second position  46 , the sliding ring  42  moves along the axis  38  in the same direction as the flow path  34 . 
     Referring again to  FIGS. 11 and 12A -B, the sliding ring  42  has a generally circular, ring-like shape having an aperture in the center. In the embodiment illustrated in  FIGS. 11 and 12A -B, the sliding ring  42  has a generally flat first surface and second surface which are connected by a curved outer and inner surface forming the ring shape. As shown in  FIGS. 11 and 12A -B, the top surface, bottom surface, inner surface, and outer surface generally have a similar width. However, it is contemplated that the widths of any of the surfaces may be larger or smaller than any other surface width of the sliding ring  42 . In the embodiment shown in  FIGS. 12A-B , the sliding ring  42  is disposed perpendicular to the axis  38  such that the axis  38  is disposed through the aperture in the center of the sliding ring  42 . However, it is contemplated that the sliding ring  42  may be various other shapes and/or orientations configured to be axially moveable along the axis  38 . 
     Referring again to the embodiment illustrated in  FIGS. 12A-B , the sliding ring  42  may include at least one, and as illustrated in  FIGS. 12A-B , a plurality of connecting prongs  48  which extend from the second surface of the sliding ring  42 . As such, it is contemplated that the connecting prongs  48  may be made of the same material as the sliding ring  42  or may be made of a different material including but not limited to steel, aluminum, or a plastic polymer as known by one of ordinary skill in the art. In the embodiment shown in  FIGS. 12A-B , the connecting prongs  48  extend the entire width of the bottom surface, however, various configurations have been contemplated. The connecting prongs  48  illustrated in  FIGS. 12A-B  are disposed in pairs about the top surface of the sliding ring  42 , having a space between each pair. However, it is also contemplated that the connecting prongs  48  may be disposed at another location of the guide vane as desired by one of ordinary skill in the art. A connecting rod  50  is configured to be disposed in the space between each pair of connecting prongs  48 . It is contemplated that a fastener is disposed through the pair of connecting prongs  48  and through the connecting rod  50  to secure the connecting rod  50  to the sliding ring  42 . However, it is also contemplated that the connecting rod  50  and the sliding ring  42  may be coupled in various other ways, as known by one of ordinary skill in the art. In the embodiment illustrated in  FIGS. 12A-B , the sliding ring  42  includes four pairs in the connecting prongs  48  corresponding to four connecting rods  50 ; however, any number of connecting prongs  48  and/or connecting rods  50  may be implemented in the airflow adjustment assembly  40 . 
     The connecting rods  50  are at least partially disposed within the interior  32  of the compressor housing  30  and are configured to move in the direction opposite the flow path  34  when the sliding ring  42  is moved to the first position  44  and move in the same direction as the flow path  34  when the sliding ring  42  is moved to the second position  46 . More specifically, the connecting rods  50  are axially movable along the axis  38  when the sliding ring  42  moves axially along the axis  38 . As illustrated in the embodiment shown in  FIGS. 12A-B , the connecting rods  50  have a generally bar-shaped main section having a circular connecting portion on each end. The circular portions are configured to allow the fastener to couple a first circular portion to the connecting prongs  48  of the sliding ring  42 . On the opposite end of the connecting rod  50  is another circular portion which may be similar or identical to the first circular portion and is configured to pivotally couple the connecting rod  50  to a guide vane  52 . Again, a fastener may be disposed through the circular portion to secure the connecting rod  50  and the guide vane  52 . The connecting rods  50  may be comprised of steel, aluminum, or another material having sufficient strength to couple the sliding ring  42  to the guide vane  52  of the air flow adjustment assembly. 
     As illustrated in the embodiments shown in  FIGS. 12A-B , the connecting rods  50  extend from the sliding ring  42  to the guide vane  52  and are configured to define a space between the sliding ring  42  and the guide vanes  52 . In the embodiment illustrated in  FIGS. 12A-B , the airflow adjustment assembly  40  includes four connecting rods  50 , however it is contemplated that more or fewer connecting rods  50  may be disposed between the sliding ring  42  and the guide vanes  52 . As additionally illustrated in the embodiment shown in  FIGS. 12A-B , a single connecting rod  50  is coupled to each guide vane  52 . However, it is additionally contemplated that multiple connecting rods  50  may be coupled to each guide vane  52  as desired by one of ordinary skill in the art. 
     Referring again to the embodiment shown in  FIGS. 12A-B , the connecting rods  50  are coupled to the guide vanes  52  at a first set of connecting protrusion  54  of the guide vane  52 . As illustrated in  FIGS. 12A-B , the first set of connecting protrusion  54  is comprised of a pair of protrusions configured to have the connecting rod  50  disposed between the pair of protrusions. The fastener is then disposed through each protrusion and the circular portion of the connecting rod  50  to pivotally couple the guide vane  52  to the connecting rod  50 . Various other configurations have also been contemplated which allow the connecting rod  50  and the guide vane  52  to be pivotally coupled to one another without departing from the spirit of the invention. Moreover, it is contemplated that the sliding ring  42  and the guide vane  52  may be coupled to one another using another mechanism without departing from the spirit of the invention. As additionally illustrated in  FIGS. 12A-B , the first set of connecting protrusions  54  are disposed between a guide base  78  and a guide tip  80  of the guide vane  52 . However, it is additionally contemplated that the first set of connecting protrusions  48  may be disposed along any portion of the guide vane  52 . 
     The sliding ring  42  is additionally coupled to a yoke  56  which is at least partially disposed with the interior  32  of the compressor housing  30 . As illustrated in  FIGS. 11 and 12A -B, the yoke  56  may have a generally semi-circle shape and is disposed in the direction opposite the direction of airflow from the sliding ring  42 . The yoke  56  is pivotally coupled to the sliding ring  42  and configured to move the sliding ring  42  axially along the axis  38  between the first position  44  and the second position  46 . It is contemplated that the yoke  56  may be a variety of other shapes or configurations configured to be pivotally coupled to the sliding ring  42  as known by one of ordinary skill in the art. The yoke  56  is typically comprised of the same material as the sliding ring  42  such as steel, aluminum or aluminum alloy, or a plastic polymer. However, the yoke  56  may be comprised of any other material as desired by one of ordinary skill in the art. 
     As shown in the embodiment illustrated in  FIGS. 12A-B ,  13  and  15 , the yoke  56  has a coupler  58  disposed on each distal end of an inside surface of the yoke  56 . Each of the couplers  58  are configured to engage a connecting pin  60  which pivotally couples the sliding ring  42  and the yoke  56 . It is contemplated that the coupler  58  is configured to allow the yoke  56  to tilt in a direction opposite the direction of the flow path  34  to move the sliding ring  42  from the first position  44  to the second position  46 . More specifically, a top portion of the yoke  56  which is disposed along the semi-circle between the two distal ends of the yoke, is configured to move in the direction opposite the direction of the flow path  34  while the ends of the yoke  56  move in the direction of the flow path  34  to move the connecting pins  60  which move the sliding ring  42  from the first position  44  to the second position  46 . 
     Referring again to the embodiment illustrated in  FIGS. 12A-B ,  13 , and  14 , the yoke  56  is coupled to the sliding ring  42  using the connecting pins  60  and the couplers  58 . It is contemplated that two connecting pins  60  may couple the sliding ring  42  and the yoke  56  as illustrated in  FIGS. 12A-B ; however, more or less connecting pins  60  may be used as desired by one of ordinary skill in the art. As also illustrated in  FIGS. 12A-B , the connecting pins  60  may be coupled to the sliding ring  42  through guide bushings. However, it is contemplated that the connecting pins  60  may be coupled to the sliding ring  42  using another method as known by one of ordinary skill in the art. It is also contemplated that the yoke  56  is coupled to the sliding ring  42  using another connection method other than the coupler  58 /connecting pin  60  mechanism as described above, as known by one of ordinary skill in the art. 
     As illustrated in the embodiment shown in  FIGS. 12A-B ,  13 , and  14  the yoke  56  may include a rectangular tab  62  disposed approximately equidistant between the two distal ends of the yoke  56  along the semi-circle. The rectangular tab  62  is configured to engage a cross-shaft  64 . The cross-shaft  64  may be composed of steel, aluminum or aluminum alloy, a plastic polymer, or any other material as known by one of ordinary skill in the art. As illustrated in the embodiment shown in  FIGS. 12A-B , the cross-shaft  64  is disposed perpendicular to the axis  38  and is fixed to the rectangular tab  62  of the yoke  56 . As illustrated in the embodiment shown in  FIGS. 12A-B ,  13 , and  14 , the rectangular tab  62  of the yoke  56  may include an aperture configured to allow a portion of the cross-shaft  64  to be disposed through the aperture. Moreover, the rectangular tab  62  may include a gap disposed above the aperture which allows the cross-shaft  64  to be inserted into the aperture. As illustrated in the embodiment shown in  FIGS. 12A-B ,  13 , and  14 , the gap may be closed or fixed be a fastener. It is also contemplated that the cross-shaft  64  and yoke  56  may be fixed in any other configuration as known by one of ordinary skill in the art including but not limited to having the cross-shaft  64  and the yoke  56  being a single integral piece. 
     As additionally illustrated in the embodiment shown in  FIGS. 12A-B ,  13 , and  14  the cross-shaft  64  is typically a cylindrical rod having two ends. However, it is contemplated that the cross-shaft  64  may be rectangular, triangular, or any other shape as desired by one of ordinary skill in the art. It is also contemplated that, as illustrated in  FIGS. 12A-B ,  13 , and  14  the cylindrical rod portion of the cross-shaft  64  may have an indented portion. The indented portion may extend around the entire circumference of the cross-shaft  64  or may only extend around a portion of the circumference of the cross-shaft  64 , as illustrated in  FIGS. 12A-B . The yoke  56  may also be attached to the cross shaft  64  by having a through hole or aperture disposed in the yoke  56  which is configured to allow the cross-shaft  64  to pass directly through the yoke  56 , as described above. Additionally, it is contemplated that the cross shaft  64  and the yoke  56  may be coupled using a clamp, an interference fit, or another connection method as known by one of ordinary skill in the art. Each end of the cross-shaft  64  may include a bushing  66  as illustrated in  FIGS. 12A-B , or may include another connection feature allowing the cross-shaft  64  to be coupled to another device. 
     In the embodiment illustrated in  FIGS. 12A-B , one end of the cross-shaft  64  includes an actuation mechanism  68 . The actuation mechanism  68  is configured to be actuated by an actuation assembly or other mechanism. When actuated, the actuation mechanism  68  is configured to rotate which in turn pulls the rectangular tab  62  of the yoke  56  such that the yoke  56  tilts and in turn moves the sliding ring  42  axially along the axis  38  from the first position  44  to the second position  46 . The actuation mechanism  68  is typically comprised of steel, however the actuation mechanism  68  may be comprised of another material which has the strength required to rotate the cross-shaft  64 , as known by one of ordinary skill in the art. As illustrated in the embodiment shown in  FIGS. 12A-B , the actuation mechanism  68  has a rectangular bottom portion which extends towards a rounded upper portion which includes an engagement protrusion for engaging another mechanism for actuation of the cross-shaft  64 . However, it is contemplated that the actuation mechanism  68  may be any other shape or configuration as desired by one of ordinary skill in the art, including but not limited to a gear or a control lever which may be actuated by a pneumatic actuator or vacuum actuator or other actuator has known by one of ordinary skill in the art. 
     Referring now to the embodiment shown in  FIGS. 15-18 , the guide vanes  52  are at least partially disposed within the interior  32  of the compressor housing  30 . The guide vanes  52  are generally comprised of steel, aluminum or aluminum alloy, a plastic polymer, or another material as known by one of ordinary skill in the art. Additionally, the guide vanes  52  have a separate outer surface  72  and an inner surface  74 . However, it is also contemplated that the guide vanes  52  may be comprised of a single piece without departing from the spirit of the invention. It is contemplated that the outer surface  72  and inner surface  74  may be comprised of the same material or the outer surface  72  and the inner surface  74  may be comprised of different materials from one another. Both the outer surface  72  and the inner surface  74  of each guide vane  52  are configured to form a seal between each of the guide vanes  52  when the sliding ring  42  is in the first position  44  and when the sliding ring  42  is in the second position  46 . 
     As illustrated in the embodiment shown in  FIGS. 15-18 , each guide vane  52  may be disposed within the interior  32  of the compressor housing  30 . In the embodiment illustrated in  FIGS. 10-20 , the guide vanes  52  are curved slightly and disposed adjacent to one another, forming a guide drum  76 . More specifically, the guide vanes  52  are curved such that the guide vanes  52  are disposed circumferentially about the axis  38  such that the guide vanes  52  form a circle having the axis  38  disposed through the center. In the embodiment illustrated in  FIGS. 12A-B , four guide vanes  52  are disposed about the axis  38  forming the guide drum  76 . However, it is contemplated that more or less guide vanes  52  may comprise the guide drum  76 . Further, the inner surfaces  74  of the guide vanes  52  define an interior of the guide drum  76  which the flow path  34  flows through. Additionally, each of the guide vanes  52  have a guide tip  80  and a guide base  78 , where each of the guide bases  78  are pivotally coupled to the air inlet portion  35 . The guide base  78  is spaced from the guide tip  80  along the axis  38 . The guide tips  80  of the guide vanes  52  define a vane diameter (VD). The vane diameter (VD) is measured from the inner surface  74  of one guide vane  52  to the inner surface  74  of an opposite guide vane  52  and is disposed perpendicular to the axis  38 . Moreover, the vane diameter (VD) is less than the inlet diameter (ID). Additionally, the vane diameter (VD) is configured to be increased when the sliding ring  42  is moved to the first position  44  and to be decreased when the sliding ring  42  is moved to the second position  46 . 
     Referring again to the embodiment illustrated in  FIGS. 15-18 , the inner surface  74  and outer surface  72  are separate surfaces and are disposed against each other, i.e. a top surface of the inner surface  74  is disposed against the bottom surface of the outer surface  72 . Each of the inner surface  74  and the outer surface  72  have four sides. The first side, the second side, and the third side form three sides of a rectangle such that the first side and the second side are disposed parallel to one another and the third side is disposed at approximately a 90 degree angle to both the first and second side. The fourth side connects the first side and the second side, however, the fourth side is angled such that the first side has a length that is longer than the second side. Additionally, the first side includes may include an indent  82 , as illustrated in  FIGS. 15-18 , which is configured to allow a support ring  83  to be disposed between the pair of connecting prongs  48  and coupled to the guide base  78 . It is also contemplated that the guide base  78  may not include an indent  82  such that the support ring  83  is coupled to the guide vane  52  using another configuration. 
     As illustrated best in  FIGS. 15, 16, and 18  the outer surface  72  and the inner surface  74  are arranged offset from one another such that the angled or fourth side of the outer surface  72  is matched up with the first side, or side parallel to the axis  38 , of the inner surface  74 . In other words, a portion of the inner surface  74  is visible from a top view, as illustrated in  FIG. 18 , and a portion of the outer surface  72  is visible when viewed from a bottom view, as illustrated in  FIG. 17 . This configuration allows the guide drum  76  to have an air-tight seal between guide vanes  52  when the sliding ring  42  is in the first position  44  and when the sliding ring  42  is in the second position  46 . Additionally, this configuration may also provide an air tight seal between the guide vanes  52  when the sliding ring  42  is being moved from the first position  44  to the second position  46  and when the sliding ring  42  is being moved from the second position  46  to the first position  44 . It is additionally contemplated that various other configurations of the guide vanes  52  may be implemented which provide an air-tight seal of the guide drum  76 . 
     As illustrated in the embodiment shown in  FIGS. 12A-B , the support ring  83  is disposed about the guide drum. In other words, the support ring  83  includes an aperture which has the guide drum disposed there through. However, it is also contemplated that the support ring  83  may be disposed such that the aperture is before or after the guide drum in the direction of the flow path. Moreover, as illustrated in  FIGS. 12A-B  the support ring  83  comprises multiple rings, and in the embodiment shown two rings. The outer ring  86  has a ring-shape and is disposed approximately equally from each point of the guide drum. Moreover, the outer ring  86  is configured to engage the compressor housing and provide support to the housing while allowing access to the compressor interior for installation assembly and repair of the compressor and of the airflow adjustment assembly. The inner ring  88  of the support ring  83  is configured to be coupled to the guide drum. In the embodiment illustrated in  FIGS. 12A-B , the inner ring  88  includes prongs extending from the inner ring  88  which are configured to engage with the connecting prongs  48  disposed on the guide base of the guide vane. However, it is additionally contemplated that the support ring  83  may be coupled to the guide drum, or another portion of the airflow adjustment assembly by another method as known by one of ordinary skill in the art. As additionally illustrated in  FIGS. 12A-B , the inner ring  88  and the outer ring  86  may be coupled to one another by a connecting portion. The connecting portion may also include an aperture which is configured to allow the connecting pin  60  to be disposed there through. As illustrated in the embodiment shown in  FIGS. 12A-B , the connecting pin  60  is disposed from the coupler  58  of the yoke  56 , through the aperture of the connecting portion of the support ring  83  where the connecting pin  60  is then coupled to the sliding ring  42 . It is also contemplated that the support ring  83  may be coupled to the sliding ring  42  or another portion of the airflow adjustment assembly  40  by another method as known by one of ordinary skill in the art. Moreover, it is contemplated that the support ring  83  is stationary when the sliding ring  42  is moved to the first position  44  and when the sliding ring  42  is moved to the second position  46 . However, it is contemplated that the support ring  83  may be movable such that the support ring  83  moves or slides when the sliding ring  42  is moved from the first position  44  to the second position  46  or from the second position  46  to the first position  44 . 
     As best illustrated in  FIGS. 15 and 17 , the connecting protrusions  54  of the guide vane  52  are coupled to either the inner surface  74  or the outer surface  72  of the guide vane  52 . However, it is also contemplated that the connecting protrusions  54  of the guide vane  52  are coupled to both the inner surface  74  and the outer surface  72  of the guide vane  52 . As additionally illustrated in  FIGS. 12A-B , the airflow adjustment assembly may include at least two sets of connecting protrusions  54 . The first set of connecting protrusions  54  are coupled to the connecting rods  50  and the sliding ring  42  and are configured to move both the inner surface  74  and the outer surface  72  of guide vane  52  as one piece when the sliding ring  42  is moved between the first position  44  and the second position  46 . It is also contemplated that the inner surface  74  and the outer surface  72  could be moved separately if desired by one of ordinary skill in the art. As illustrated in  FIGS. 12A-B , the first set of connecting protrusions  54  of the guide vane  52  are disposed between the guide base  78  and the guide tip  80 . In the embodiment illustrated in  FIGS. 12A-B , the first set of the connecting protrusions  54  of the guide vane  52  are disposed approximately halfway between the guide base  78  and the guide tip  80 . However, it is additionally contemplated that various other configurations of the guide vane  52  and connecting protrusions  54  may be implemented without departing from the spirit of the invention which allow the inner surface  74  and the outer surface  72  of the guide vanes  52  to be coupled to the connecting rods  50 . 
     As illustrated in the embodiment shown in  FIGS. 12A-B , the second set of connecting protrusions  54  are disposed at the guide base  78  of the guide vane  52 . Again, it is contemplated that the connecting protrusions  54  may be made of the same material as the guide vane  52  or may be made of a different material including but not limited to steel, aluminum, or a plastic polymer as known by one of ordinary skill in the art. Moreover, the second set of connecting protrusions  54  disposed in pairs about the top surface of the guide vane  52 , having a space between each pair. As illustrated in  FIGS. 12A-B , a portion of the support ring  83  is disposed between the second set of connecting protrusions  54  and the support ring  83  and the connecting protrusions  54  may be secured by a fastener in a similar fashion as described above. However, it is also contemplated that the support ring  83  and the connecting protrusions  54  may be coupled in various other ways, as known by one of ordinary skill in the art. In the embodiment illustrated in  FIGS. 12A-B , the guide vane includes four pairs in the second set of connecting protrusions  54  corresponding to four connecting portions of the support ring  83 ; however, any number of connecting protrusions  54  may be implemented in the airflow adjustment assembly  40 . As additionally illustrated in  FIGS. 12A-B , the second set of connecting protrusions  54  are disposed on the guide base of the guide vane  52 . However, it is also contemplated that the second set of connecting protrusions  54  may be disposed on any portion of the guide vane  52 . 
     Referring now to the embodiment shown in  FIGS. 19 and 20 , in operation, the sliding ring  42  begins in the first position  44  shown in  FIG. 19 . When the sliding ring  42  is in the first position  44 , the yoke  56  is disposed perpendicular to the axis  38  while the actuation mechanism  68  of the cross-shaft  64  is not actuated, as illustrated in  FIG. 19 . However, it is also contemplated that when the sliding ring  42  is in the first position  44 , the yoke  56  may be disposed at an angle which is negative or positive relative to the axis. Additionally, when the sliding ring  42  is in the first position  44 , the vane diameter (VD) is at its largest such that the air flow is not restricted in the flow path  34  through the airflow adjustment device. As illustrated in  FIG. 19 , the vane diameter (VD) is at its largest when the guide vanes  52  extend parallel to axis  38 , however, it is also contemplated that the largest diameter may occur when the guide vanes  52  extend at an angle either above parallel to the axis  38 . When desired, the actuation mechanism  68  may be activated by any actuator as known by one of ordinary skill in the art. When the actuation mechanism  68  is activated, the cross-shaft  64  rotates which moves the yoke  56 . The yoke  56  is moved or tilted to an angle which may be positive or negative relative to the axis  38 . The angle may be a slight angle such as between 5 and 15 degrees or may be a bigger angle such as between 5 and 45 degrees. It is additionally contemplated that the yoke  56  may be rotated up to 90 degrees as desired by one of ordinary skill in the art. Moreover, it is also contemplated that any of the angles described may be negative angles with respect to the position of the yoke  56  when the sliding ring  42  is in the first position  44 . When the yoke  56  is moved, the connecting pins  60  push the sliding ring  42  in a direction of the flow path  34  along the axis  38  and into the second position  46 . In the second position  46 , the sliding ring  42  engages the connecting rods  50  which allow the guide vanes  52  to pivot towards the center of the guide drum  76  such that the vane diameter (VD) is decreased. As illustrated in  FIG. 20 , when the sliding ring  42  is in the second position  46  the vane diameter (VD) is decreased from when the sliding ring  42  is in the first position  44  such that the air is at least partially restricted from flowing through the interior  32  of the compressor along the flow path  34 . When the sliding ring  42  is in the first position  44  and when the sliding ring  42  is in the second position  46 , the guide vanes  52  are sealed to one another such that no air escapes between the guide vanes  52  and all of the air entering the airflow adjustment assembly  40  moves through the airflow adjustment assembly  40  and exits the airflow adjustment assembly  40  to the compressor housing  30 . 
     It is also contemplated that, when desired, the sliding ring  42  can be moved from the second position  46  to the first position  44 . To achieve this, the actuation mechanism  68  of the cross-shaft  64  may be engaged by a mechanism which rotates the cross-shaft  64  to the position illustrated in  FIG. 19 . The yoke  56  is then moved to be perpendicular to the axis  38 . The connecting pins  60  pull the sliding ring  42  to the first position  44 . When the sliding ring  42  is moved to the first position  44 , the connecting rods  50  are engaged and pivot the guide vanes  52  away from the center of the guide drum  76  until the vane diameter (VD) is at its largest. Moreover, it is contemplated that the vane diameter (VD) may be held in any position between the position corresponding with the first position  44  of the sliding ring  42  and the position corresponding with the second position  46  of the sliding ring  42 . As illustrated in the Figures, the sliding ring  42  is disposed about the guide drum  76  in both the first position  44  and the second position  46 . 
     One advantage of controlling the vane diameter (VD) is to achieve higher pressure ratios at a low engine speed. This improves the map width of a single compressor and increases the surge line of the compressor which allows better operating efficiency of the compressor and better intake throttling. By controlling the vane diameter (VD) in a single stage compressor by the method and apparatus described above, a similar performance of a multiple stage compressor may be achieved with the space saving advantages that come with a single stage compressor. The apparatus and method as described above also allow the turbocharger to achiever higher Exhaust Gas Recirculation (EGR) rates without impacting power rating. Additionally, the apparatus as described above may increase Low End Torque (LET) which would allow engine downsizing. 
     The invention has been described in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. Many modifications and variations of the present invention are possible in light of the above teachings, and the invention may be practiced otherwise than as specifically described.