Abstract:
A variable displacement compressor is disclosed. The compressor includes a crankcase for receiving a fluid. The crankcase has a plurality of compression chambers in which the fluid is compressed. A plurality of pistons disposed within the crankcase and are configured for reciprocal movement within the plurality of chambers to compress and pump the fluid. Further, a rotor assembly having a drive shaft and a rotor, wherein the rotor has a first pivot arm support member extending from a first surface of the rotor. A sleeve is slidably engaged with the drive shaft and configured for axial movement along a longitudinal axis of the drive shaft. A swash ring is coupled to the plurality of pistons and to the rotor by means of a pivot arm. Rotary motion of the swash ring and rotor causes reciprocal motion of the plurality of pistons within the plurality of chambers.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to variable displacement compressors having an adjustable swash ring for changing the displacement of the compressor. 
       BACKGROUND OF THE INVENTION 
       [0002]    Variable displacement compressors having a swash ring are well known in the art. Such compressors typically include a plurality of pistons that are driven by the swash ring. The swash ring is operatively coupled to a drive shaft and rotor assembly. The swash ring is angled or inclined relative to the rotor to change the total displacement of the compressor. One well known design includes a pivot pin that is fixed at one end to the drive shaft and pivotally connected to the swash ring at the other end. 
         [0003]    Conventional swash ring compressors rely on a sphere to contact the inside of the swash ring supporting the load. Although this design works when the swash ring is made from a hard material, a swash ring made from soft alloys is preferred for improved seizure resistance. To allow a swash ring compressor to use a soft alloy for the swash ring, the load must be distributed over a larger area, which reduces the contact pressure. 
         [0004]    While this design achieves its intended purpose many problems still exist. For example, because the pivot pin is located in the drive shaft, the drive shaft must be thicker or larger in diameter resulting in a higher design cost. Moreover, since the swash ring is limited by the pin thickness the compressor will have a large diameter but a poor volumetric efficiency. Further, prior art designs are unable to maintain a constant TDC without holding extremely tight positional tolerances. Further, inserting the pivot pin into the drive shaft at an angle requires expensive gauging. Since a single pivot pin carries the entire load, the pivot pin needs to be made of very expensive heat treated special steels. In addition, designs that include a single pin at a specified angle are not bidirectional thus, clockwise and anticlockwise models must be produced. This of course adds cost and manufacturing complexity. The design further has no provision for a counterweight balancing mass and lacks room for packaging such a mass to offset the pivot pin structure. 
         [0005]    For these reasons and others a new and improved swash ring compressor is needed. Such a compressor is herein described below. 
       BRIEF SUMMARY OF THE INVENTION 
       [0006]    In an aspect of the present invention, a variable displacement compressor is provided. The compressor includes a crankcase for receiving a fluid. The crankcase has a plurality of compression chambers in which the fluid is compressed. A plurality of pistons are disposed within the crankcase and configured for reciprocal movement within the plurality of chambers to compress and pump the fluid. 
         [0007]    The compressor may further include a pivot pin projecting from the drive shaft with a sleeve disposed over the spherical end of the pivot pin. The sleeve being pivotably arranged about the spherical end of the pivot pin and slidably engaged within a swash ring. The compressor may further include a rotor assembly having a drive shaft and a rotor wherein the rotor has a first pivot arm support member extending from a first surface of the rotor; a sleeve slidably engaged to the drive shaft and configured for axial movement along a longitudinal axis of the drive shaft. The swash ring is coupled to the plurality of pistons and through rotary motion of the swash ring causes reciprocal motion of the plurality of pistons within the plurality of chambers, and wherein the swash ring is connected to the rotor by a first pivot arm pivotally connected to a swash ring at a first end and to the first pivot support member at a second end, and wherein the swash ring is pivotally mounted to the sleeve, whereby axial movement of the sleeve along the longitudinal axis of the drive shaft causes the swash ring to tilt relative to the rotor. 
         [0008]    In yet another aspect of the present invention, the compressor includes a spring disposed around the drive shaft for biasing the swash ring away from the rotor. 
         [0009]    In yet another aspect of the present invention, the compressor includes a counterweight member extending from the first surface of the rotor to counter balance the centrifugal forces created by the rotation of the swash ring. 
         [0010]    In still another aspect of the present invention, the counterweight member extending from the first surface of the rotor is disposed opposite the pivot arm support member. 
         [0011]    In still another aspect of the present invention, the counterweight member extending from the first surface of the rotor and is disposed inward of the swash ring. 
         [0012]    In yet another aspect of the present invention, the compressor includes a thrust bearing to provide axial movement of the swash ring along the drive shaft toward the rotor. 
         [0013]    In yet another aspect of the present invention, the compressor includes a swash ring stop member extending from the first surface of the rotor to prevent angular rotation of the swash ring past a predefined angle. 
         [0014]    In still another aspect of the present invention, the first end of the first pivot arm is spherically shaped. 
         [0015]    In still another aspect of the present invention, the second end of the first pivot arm is cylindrically shaped. 
         [0016]    In yet another aspect of the present invention, the compressor includes an insert sleeve press fitted into a bore in the swash ring for receiving the first end of the first pivot arm. 
         [0017]    In yet another aspect of the present invention, a variable displacement compressor is provided. The compressor includes a crankcase for receiving a fluid, wherein the crankcase has a plurality of compression chambers in which the fluid is compressed. Further, a plurality of pistons are disposed within the crankcase and configured for reciprocal movement within the plurality of chambers to compress and pump the fluid. A rotor assembly is further provided having a drive shaft and a rotor. The rotor has a pivot arm support member extending from a first surface of the rotor. A sleeve is slidably engaged to the drive shaft and configured for axial movement along a longitudinal axis of the drive shaft. A swash ring is coupled to the plurality of pistons and through rotary motion of the swash ring causes reciprocal motion of the plurality of pistons within the plurality of chambers. The swash ring is connected to the rotor by a pair of pivot arms pivotally connected to the swash ring at a first end and to the pivot support member at a second end. Further, the swash ring is pivotally mounted to the sleeve, whereby axial movement of the sleeve along the longitudinal axis of the drive shaft causes the swash ring to tilt relative to the rotor. 
         [0018]    The compressor may further contain a rotor assembly having a drive shaft and a rotor, wherein the rotor has a first pivot arm support member extending from a first surface of the rotor; a sleeve slidably engaged to the drive shaft and configured for axial movement along a longitudinal axis of the drive shaft; and a swash ring coupled to the plurality of pistons and through rotary motion of the swash ring causes reciprocal motion of the plurality of pistons within the plurality of chambers. Wherein the swash ring is connected to the rotor by a first pivot arm pivotally connected to the swash ring at a first end and to the first pivot support member at a second end, and wherein the swash ring is pivotally mounted to the sleeve, whereby axial movement of the sleeve along the longitudinal axis of the drive shaft causes the swash ring to tilt relative to the rotor. 
         [0019]    In yet another aspect of the present invention, the compressor includes a second pivot arm for connecting the swash ring to the rotor. 
         [0020]    In yet another aspect of the present invention, the compressor includes a second pivot arm support member fixed to the rotor for supporting the second pivot arm. 
         [0021]    In yet another aspect of the present invention, a variable displacement compressor is provided. The compressor includes a crankcase for receiving a fluid, wherein the crankcase has a plurality of compression chambers in which the fluid is compressed. Further, a plurality of pistons are disposed within the crankcase and configured for reciprocal movement within the plurality of chambers to compress and pump the fluid. A rotor assembly is further provided having a drive shaft and a rotor. The rotor has a pivot arm support member extending from a first surface of the rotor. A sleeve is slidably engaged to the drive shaft and configured for axial movement along a longitudinal axis of the drive shaft. A swash ring is coupled to the plurality of pistons and through rotary motion of the swash ring causes reciprocal motion of the plurality of pistons within the plurality of chambers. The swash ring is connected to the rotor by a pair of pivot arms pivotally connected to the swash ring at a first end and to the pivot support member at a second end. Further, the swash ring is pivotally mounted to the sleeve, whereby axial movement of the sleeve along the longitudinal axis of the drive shaft causes the swash ring to tilt relative to the rotor. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]      FIG. 1  is a perspective view of a variable displacement swash ring type compressor, in accordance with an embodiment of the present invention; 
           [0023]      FIG. 2  is a side perspective view of the swash ring and rotor assembly of the variable displacement compressor shown in  FIG. 1 , wherein the swash ring is shown in a minimum displacement position, in accordance with an embodiment of the present invention; 
           [0024]      FIG. 3  is a side perspective view of the swash ring and rotor assembly of the variable displacement compressor, wherein the swash ring is shown in a maximum displacement position, in accordance with an embodiment of the present invention; 
           [0025]      FIG. 4  is a cross-sectional view through the swash ring and rotor assembly of the variable displacement compressor, wherein the swash ring is shown in a maximum displacement position, in accordance with an embodiment of the present invention; 
           [0026]      FIG. 5  is a perspective view of the rotor of the rotor assembly, in accordance with an embodiment of the present invention; 
           [0027]      FIG. 6  is a perspective view of a swash ring and the rotor assembly, in accordance with an embodiment of the present invention; and 
           [0028]      FIG. 7  is a perspective view of an alternate embodiment of a rotor and swash ring, in accordance with the present invention; 
           [0029]      FIG. 8  is a cross-sectional view of an alternate swash ring, in accordance with an alternate embodiment of the present invention; 
           [0030]      FIG. 9  is a cross-sectional view of an alternate embodiment of a swash ring and rotor, in accordance with an alternate embodiment of the present invention; 
           [0031]      FIG. 10  is a cross-sectional view of a sleeve that distributes the load on the swash ring, in accordance with an alternate embodiment of the present invention; and 
           [0032]      FIG. 11  is a perspective view of the pin that supports the swash ring, in accordance with an alternate embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0033]    Referring now to  FIG. 1  a variable displacement compressor  10  is illustrated, in accordance with an embodiment of the present invention. Compressor  10  is referred to as a variable displacement compressor because the total displacement of the refrigerant pumping capacity may be adjusted by changing the inclination of a swash ring  11 , which will be described in further detail below. Variable displacement compressor  10  includes a crankcase  12  that has a plurality of chambers  14  configured to cooperate with a plurality of pistons  16 . Pistons  16  are operatively coupled to a swash ring  11  to cause reciprocal movement of pistons  16  within chambers  14 . Compressor  10  further includes a rotor assembly  20  having a rotor  22  rotationally fixed to a drive shaft  24 . Rotor assembly  20  imparts a rotational force to swash ring  11  to cause rotary movement of the swash ring. Typically, drive shaft  24  will have a pulley (not shown) mounted to one of its ends. A serpentine belt driven by an engine of an automotive vehicle engages the pulley and rotationally drives the pulley, although, the concepts of the present invention will be realized on a compressor where the drive shaft is driven by other means. 
         [0034]    Referring to  FIG. 2 , swash ring  11  and rotor assembly  20  are illustrated in further detail, in accordance with an embodiment of the present invention. Swash ring  11  is shown in a plane that is parallel with the base  36  of rotor  22 . When swash ring  11  is in the position shown in  FIG. 2 , compressor  10  is at its minimum displacement. Rotor assembly  20  further includes a sleeve  26 . Sleeve  26  is operatively configured to slide axially along drive shaft  24 . Swash ring  11  is pivotably secured to sleeve  26  through a plurality of pivot pins  28 . While only one pivot pin  28  is illustrated, it should be understood that a similarly configured pivot pin (not shown) is disposed on the opposite side of drive shaft  24 . Pivot pins  28  are axially aligned with one another and extend radially outward from diametrically opposed sides of sleeve  26 . The pivot pins  28  pivotally engage the swash ring  11  to allow the swash ring to pivot about an axis running longitudinally through pivot pins  28  and through driveshaft  24 . 
         [0035]    Further, swash ring  11  is pivotally mounted to rotor  22  to allow the swash ring to rotate relative to rotor  22 , as will be described in greater detail below. The angle of inclination of swash ring  11  relative to rotor  11  increases as sleeve  26  approaches rotor  22 . Swash ring  11  is biased away from rotor  22  by a biasing spring  30  disposed around drive shaft  24 . More specifically, spring  30  contacts rotor  22  at a first end  32  and sleeve  26  at a second end  34 . As sleeve  26  moves closer to rotor  22  spring  30  compresses. Conversely, as sleeve  26  moves away from rotor  22  spring  30  expands in length. 
         [0036]    Referring now to  FIG. 3 , a perspective view of swash ring  11  and rotor assembly  20  is illustrated, in accordance with an embodiment of the present invention. Swash ring  11  is shown in an inclined position relative to the rotor base  36 . The inclination of swash ring  11  is provided by the axial sliding movement of sleeve  26  along drive shaft  24  in a direction that compresses spring  30 . 
         [0037]    Referring now to  FIG. 4 , the attachment of swash ring  11  to rotor assembly  20  is further illustrated in a cross-sectional view as indicated in  FIG. 3 , in accordance with an embodiment of the present invention. Swash ring  11  is mounted to rotor  22  by a pair of pins  40  disposed adjacent on another (as shown in  FIG. 5 ). Each pin  40  is secured or press fitted into bores  42  disposed in a pin support member  44  at a first end  46  of each pin  40 . Pin support member  44  is preferably integrally formed and extends from base  36  of rotor  22 . Each pin  40  is slidably and pivotably coupled to swash ring  11  at opposing ends  48 . More specifically, each opposing end  48  is preferably spherical and is fitted into a collar or guide bushing  50  having spherical sidewalls  52  that cooperatively mate with spherical surfaces of end  48 . Each collar bushing  50  is configured to slide within a bore  54  of swash ring  11 . In operation, as sleeve  26  slides away from rotor  22  causing swash ring  11  to move toward a plane that is parallel to base  36  of rotor  22 , as shown in  FIG. 2 , swash ring  11  moves over each collar bushing  50 . In this manner, swash ring  11  is allowed to move between an inclined plane and a plane that is parallel with base  36  of rotor  22 . 
         [0038]    Referring now to  FIG. 5 , rotor  22  is illustrated in further detail, in accordance with an embodiment of the present invention. As previously stated, rotor  22  includes a pin support member  44  that extends from base  36  of rotor  22 . Support member  44  supports pins  40  at a predefined angle. While two support pins  40  are illustrated, the present invention contemplates the use of one pin as well as more than two pins to support swash ring  11 . Rotor  22  further includes a pair of sleeve stops  60  and  62 . Sleeve stops prevent further movement of sleeve  26  toward rotor  22 . When sleeve  26  is stopped by sleeve stops  60  and  62 , the variable displacement compressor is in a maximum displacement configuration. Rotor  22  further includes a counterweight structure  64 . Counterweight structure  64  is a mass of material (i.e., metal) that extends from the base  36  of rotor  22 . Counterweight  64  counters the centrifugal forces generated by the rotation of rotor  22  and the mass making up support pin structure  44 . Effectively, counterweight  64  balances out the centrifugal forces generated by the rotation of pin support structure  44 . 
         [0039]    Referring now to  FIG. 6 , a perspective view of swash ring  11  and rotor assembly  20  is shown, in accordance with an embodiment of the present invention. Swash ring  11  is at an inclination that causes the maximum displacement of refrigerant. At maximum displacement, sleeve stops  60  and  62  are shown in contact with an arm  70  integrally formed in and extending from sleeve  26 . This configuration allows sleeve  26  to move toward rotor  22  and compressing spring  30  until the surface  72  of arm  70  contacts sleeve stop  60  or  62 . Of course, the present invention contemplates the use of only one sleeve stop instead of two. 
         [0040]    Referring now to  FIG. 7 , a perspective view of an alternate embodiment of a rotor  100  and swash ring  102  are illustrated, in accordance with another embodiment of the present invention. As in rotor  22  described above, rotor  100  includes a pin support member  44 ′ that extends from base  36 ′ of rotor  100 . Support member  44 ′ supports a pair of pins  104  at a predefined angle. While two support pins  104  are illustrated, of course, the present invention contemplates the use of one pin as well as more than two pins to support swash ring  102 . Rotor  100  further includes a pair of sleeve stops  106  (one shown). Sleeve stops are configured and operate in the same manner as previously described with reference to rotor  22  shown in  FIG. 5 , that is to prevent further movement of sleeve  26  (shown in  FIG. 2 ) toward rotor  100 . Rotor  100  further includes a counterweight structure (not shown) having the same configuration as described and illustrated above with respect to rotor  22  (shown in  FIG. 5 ). 
         [0041]    With continuing reference to  FIG. 7 , the attachment of swash ring  102  to rotor  100  will now be described. Swash ring  102  includes an elongated aperture  108  that extends through swash ring  102 . A tube bushing  110  is disposed in elongated aperture  108 . Elongated aperture  108  is configured such that the outer surfaces of tube bushing  110  contact the inside surface of aperture  108  and allows swash ring  102  to rotate relative to tube bushing  110 . Support pins  104  are substantially straight pins with a step  112  to prevent tube bushing  110  from sliding towards support member  44 ′. Further, support pins  104  include an annular groove  114  for lockably receiving a c-clamp  116  or similar device to secure tube bushing  110  to support pins  104 . This configuration provides an efficient means to rotatably attach the swash ring to the rotor. 
         [0042]    Referring now to  FIG. 8 , a cross-sectional view of an alternate swash ring  200  is illustrated in accordance with an alternate embodiment of the present invention. As shown in  FIG. 8 , swash ring  200  includes a support sleeve  202 . Support sleeve  202  is press fitted into a bore  204  in swash ring  200 . A pin (not shown) similar to pin  40  having a spherical end  48 , as shown in  FIG. 4 , is configured to support swash ring  200  around drive shaft  24 . In operation, the spherical end  48  of pin  40  slides along the inside surface of support sleeve  202 . A flared end  206  of bore  204  allows the swash ring to tilt with out interfering with pin  40 . Support sleeve  202  operates to distribute the load on pin  40  over a larger surface area of the swash ring  200 . 
         [0043]    Referring now to  FIG. 9 , a cross-sectional view of an alternate embodiment of a swash ring and rotor assembly generally referenced at  300  is shown. As in the above described embodiments, assembly  300  has a drive shaft  302 , a swash ring  304  and a rotor  306 . Swash ring  304  is supported around driveshaft  302  by a pin  308 . Pin  308  has a straight end  310  that is press fitted into a bore  312  in driveshaft  302 . Pin  308  also includes a spherical portion  314  opposite straight end  310 . Spherical portion  314  is disposed in a bore  316  disposed in swash ring  304 . Further, a sleeve  318  is provided that is press fitted into bore  316 . Sleeve  318  has mating surfaces  320  that have a similar shape and profile (i.e. spherical) as spherical portion  314 . Thus, in operation, swash ring  304  will pivot about spherical portion  314  changing its angle of inclination relative to the driveshaft  302 . 
         [0044]    Referring now to  FIGS. 10 and 11 , a cross-sectional view of sleeve  318  and a perspective view of pin  308  are shown. Sleeve  318 , as referenced above, includes mating surfaces  320  that cooperate with spherical end  314 . Additionally, sleeve  318  has a flared end  322  that allows swash ring  304  to change its angle of inclination relative to driveshaft  302  without interfering with pin  308 . The outer surface  324  of sleeve  318  cooperates with bore  316  to secure sleeve  318  within bore  316 , for example, by press fitting. Pin  308  includes spherical portion  314 , as stated above. However, the present invention contemplates that spherical portion  314  need not include the terminal end of pin  308 . In other words, spherical portion  314  may be located anywhere along pin  308  to allow swash ring  304  to rotate about spherical portion  314 . Adjacent spherical portion  314  is a tapered portion  326  that cooperates with flared end  322  of sleeve  318  to prevent pin  308  from contacting swash ring  304  and sleeve  318  when the swash ring changes its angle of inclination relative to driveshaft  302 . 
         [0045]    The pin structures described in the various embodiments above allow the load from the swash ring to be distributed over a large area. In a preferred embodiment of the present invention, the swash rings described above are made of soft materials such as aluminum, copper alloys and powder metals. Swash rings made of these soft materials exhibits good bearing properties. 
         [0046]    The forgoing description discloses various embodiments, and modifications thereof, of the present invention. One skilled in the art will readily recognize from such disclosure, and from the accompanying drawings and claims, that changes and variations can be made to the invention without departing from the true spirit and fair scope of the invention as defined in the following claims.