Abstract:
A scroll compressor ( 10 ) includes a housing ( 11 ) with a stationary scroll member ( 13 ) mounted therein and a swivel scroll member ( 12 ) positioned in the housing and cooperating with the stationary scroll member to form a compression chamber ( 16 ). A thrust bearing has a first bearing ring ( 40 ) for attachment to the housing ( 11 ) and having a plurality of circular bearing races ( 42,54 ), a second bearing ring ( 45 ) for attachment to the swivel scroll member ( 12 ) and having a plurality of circular bearing races ( 47,55 ), and a plurality of balls ( 56 ) retained between the rings in associated pairs of the races. The races can have rounded tip ( 50,51 ), pointed tip ( 57,59,60,61,62 ), plateau ( 52,53 ) or flat center ( 54,55 ) portions. The first bearing ring ( 40 ) can have a thickness (C) different than a thickness (D) of the second earing ring.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a thrust ball bearing positioned between two members carrying out eccentric rotating movements relative to one another, such as a swivel scroll member and a stationary scroll member in a vehicle air conditioning scroll compressor. 
     In the FIGS. 1-3, there is shown a known scroll compressor  10  including a housing  11  in which are positioned a swivel scroll member  12  and a stationary scroll member  13 . The stationary scroll member  13  is fixed to the housing  11  and the swivel scroll member is free to rotate inside the housing  11 . The swivel scroll member  12  is provided with spiral partitions  14  extending toward the stationary scroll member  13  and the stationary scroll member  13  is provided with spiral partitions  15  extending toward the swivel scroll member  12 . The partitions  14  and cooperate to form a compression chamber  16  having a capacity that is varied in accordance with the eccentric rotations of the swivel scroll member  12  with respect to the stationary scroll member  13  thereby compressing a fluid in the compression chamber  16 . 
     A central axis  17  of the swivel scroll member  12  is aligned with a longitudinal axis of an eccentric end  18  of a drive shaft  19  rotated by a drive motor  20 . The drive shaft  19  has a main longitudinal axis  21  that is offset from the central axis  17  by a distance “A” such that as the drive motor  20  rotates the drive shaft  19 , the swivel scroll member  12  eccentrically rotates at a swivel radius equivalent to the eccentricity amount “A”. During operation, a thrust load is imposed in an axial direction upon the rotating swivel scroll member  12  by compression cycles of the fluid in the compression chamber  16 . In order to support the thrust load, a thrust ball bearing  22  is disposed between the swivel scroll member  12  and the housing  11 . 
     The bearing  22  includes a pair of bearing rings  23  having the same shape and same dimension and a plurality of balls  24  disposed between the bearing rings. As shown in the FIG. 2, the bearing rings  23  each have a generally planar annular body  25  with a plurality of annular bearing races  26  open to one planar surface  27 . The races  26  are formed as depressions or grooves in the surface  27 . As shown in the FIG. 1, one of the rings  23  is mounted in an annular recess  28  formed in a surface of the housing  11  facing the swivel scroll member  12  and the other ring  23  is mounted in a similar recess  29  formed in a surface of the swivel scroll member  12  facing the housing  11 . 
     The balls  24  are retained in the facing races  26  as shown in the FIGS. 1 and 3. The balls  24  in the respective races  26  roll on a pitch circle  30  corresponding to the eccentric rotations of the swivel scroll member  12 . The pitch circle  30  is the lowest portion of the race wall which is curved at a predetermined radius. A diameter “B” of the pitch circle  30  is equal to the eccentricity distance “A”. 
     In the conventional thrust ball bearing  22 , the bearing rings  23  are of the same shape and same dimensions, and the groove curvatures of the races  26  are the same. The curvatures of the races  26  have a larger radius than a radius of the balls  24  to decrease the contact pressures with the balls to increase the service life thereof. The use of identical rings  23  decreases manufacturing, assembly and replacement parts costs. 
     However, manufacturing tolerances may cause the races  26  to be misaligned upon assembly of the bearing  22 . One known solution to this problem is to make the radius of curvature of one of the races  26  larger than the radius of curvature of the facing race to accommodate axial misalignment. If the smaller and larger diameter races are alternated, a pair of identical rings can be utilized in the thrust bearing assembly. 
     It is also known to make the rings  23  of different thickness. 
     SUMMARY OF THE INVENTION 
     The present invention concerns a thrust bearing for a scroll compressor having a housing with a stationary scroll member mounted therein and a swivel scroll member positioned in the housing and cooperating with the stationary scroll member to form a compression chamber. The thrust bearing includes a first stationary bearing ring for attachment to the housing and having a plurality of circular bearing races, a second swivel bearing ring for attachment to the swivel scroll member and having a plurality of circular bearing races, and a plurality of balls retained between the rings in associated pairs of the races. The circular races each have a center portion that can be a rounded tip, a pointed tip, a plateau or a flat shape. The first stationary bearing ring can have a thickness different than a thickness of the second swivel bearing ring, for example, the first ring is thinner than the second ring. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above, as well as other advantages of the present invention, will become readily apparent to those skilled in the art from the following detailed description of a preferred embodiment when considered in the light of the accompanying drawings in which: 
     FIG. 1 is a cross-sectional view showing the thrust ball bearing in a prior art scroll compressor; 
     FIG. 2 is a plan view showing the bearing ring of the prior art scroll compressor shown in the FIG. 1; 
     FIG. 3 is an enlarged cross-sectional view showing a portion of the prior art thrust ball bearing shown in the FIG. 1; 
     FIG. 4 is a top plan view of a stationary bearing ring according to the present invention for the stationary scroll member of a scroll compressor; 
     FIG. 5 is a cross-sectional view of the stationary bearing ring taken along the line  5 — 5  in the FIG. 4; 
     FIG. 6 is a top plan view of a swivel bearing ring according to the present invention for the swivel scroll member of a scroll compressor; 
     FIG. 7 is a cross-sectional view of the swivel bearing ring taken along the line  7 — 7  in the FIG. 6; 
     FIG. 8 is enlarged fragmentary cross-sectional view of the races of the rings shown in the FIGS. 4-7 positioned to cooperate with a ball; 
     FIG. 9 is an enlarged fragmentary cross-sectional view similar to the FIG. 8 showing an alternate embodiment of the present invention; 
     FIG. 10 is an enlarged fragmentary cross-sectional view similar to the FIG. 8 showing a second alternate embodiment of the present invention; 
     FIG. 11 is an enlarged fragmentary cross-sectional view similar to the FIG. 8 showing a third alternate embodiment of the present invention; 
     FIG. 12 is an enlarged fragmentary cross-sectional view similar to the FIG. 8 showing a fourth alternate embodiment of the present invention; 
     FIG. 13 is an enlarged fragmentary cross-sectional view similar to the FIG. 8 showing a fifth alternate embodiment of the present invention; and 
     FIG. 14 is an enlarged fragmentary cross-sectional view similar to the FIG. 8 showing a sixth alternate embodiment of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention concerns a thrust ball bearing for a scroll compressor. There is shown in the FIGS. 4-5 a stationary bearing ring  40  according to the present invention that can be, for example, mounted on the stationary scroll member  13  shown in the FIG. 1 in place of the bearing ring  23 . 
     The bearing ring  40  has a generally planar annular body  41  with a plurality of generally annular bearing races  42  formed in one planar surface  43 . The bearing races  42  are of uniform shape and dimensions and are equally spaced in a circle. A pair of opposed mounting apertures  44  are formed in the body  41  between the races  42  and an outer periphery of the body. Pins (not shown) cooperate with the apertures  44  to secure the bearing ring  40  on a stationary scroll member such as the member  13  shown in the FIG.  1 . 
     There is shown in the FIGS. 6-7 a swivel bearing ring  45  according to the present invention that can be, for example, mounted on the swivel scroll member  12  shown in the FIG. 1 in place of the bearing ring  23 . The bearing ring  45  has a generally planar annular body  46  with a plurality of generally annular bearing races  47  formed in one planar surface  48 . The bearing races  47  are of uniform shape and dimensions and are equally spaced in a circle. A pair of opposed mounting apertures  49  are formed in the body  46  between the races  47  and an inner periphery of the body. Pins (not shown) cooperate with the apertures  49  to secure the bearing ring  45  on a swivel scroll member such as the member  12  shown in the FIG.  1 . 
     Portions of the rings  40  and  45  including the races  42  and  47  respectively are shown in more detail in the FIG. 8 that is a view similar to the FIG.  3 . The races  42  and  47  are substantially identical in shape and dimensions for receiving a ball (not shown) such as the ball  24  shown in the FIG.  3 . The rings  40  and  45  can be formed of any suitable material and can be formed of different materials. The races  42  and  47  are each formed with a predetermined radius of curvature defining a race wall. The diameter “B” of the track of the race  42 , the distance between opposed low points, is such that a rounded tip center  50  is formed at the center of the track slightly below the surface  43 . The race  47  is formed with a similar rounded tip center  51 . However, the body  41  has a different thickness than the body  46 . The body  41  has a relatively uniform thickness “C” and the body  46  has a relatively uniform thickness “D” with the thickness “D” being substantially larger than the thickness “C”. 
     There is shown in the FIG. 9 a first alternate embodiment of the present invention wherein similar parts are identified with the reference numerals used in the FIG. 8 and a suffix “a”. The races  42   a  and  47   a  are substantially identical in shape and dimensions for receiving a ball (not shown) such as the ball  24  shown in the FIG.  3 . The body  41   a  has a relatively uniform thickness “C” and the body  46   a  has a relatively uniform thickness “D” with the thickness “D” being substantially larger than the thickness “C”. Furthermore, the race  42   a  is formed with a flat or plateau center  52  and the race  47   a  is formed with a similar upstanding plateau center  53 . 
     There is shown in the FIG. 10 a second alternate embodiment of the present invention wherein similar parts are identified with the reference numerals used in the FIG. 8 and a suffix “b”. A race  54  formed in the body  41   b  and a race  55  formed in the body  46   b  are substantially identical in shape and dimensions for receiving a ball (not shown) such as the ball  24  shown in the FIG.  3 . The races  54  and  55  are formed as circular depressions without an upstanding portion so that there is a flat center of the diameter “B”. The body  41   b  has a relatively uniform thickness “C” and the body  46   b  has a relatively uniform thickness “D” with the thickness “D” being substantially larger than the thickness “C”. 
     There is shown in the FIG. 11 a third alternate embodiment of the present invention wherein similar parts are identified with the reference numerals used in the FIG. 8 and a suffix “c”. The race  47   c  is substantially identical in shape to the race  47  shown in the FIG. 8 for receiving a ball  56  such as the ball  24  shown in the FIG.  3 . The body  41   c  has a relatively uniform thickness “C” and the body  46   c  has a relatively uniform thickness “D” with the thickness “D” being substantially larger than the thickness “C”. The race  42   c  is formed with a pointed tip  57  at the center thereof. The pointed tip center  57  is formed by extending the wall of the race  42   c  inwardly tangent from a point at an angle “α” from the lowest point of the track. 
     There is shown in the FIG. 12 a fourth alternate embodiment of the present invention wherein similar parts are identified with the reference numerals used in the FIG. 8 and a suffix “d”. The race  47   d  is substantially identical in shape to the race  47  shown in the FIG. 8 for receiving the ball  56 . The body  41   d  has a relatively uniform thickness “C” and the body  46   d  has a relatively uniform thickness “D” with the thickness “D” being substantially larger than the thickness “C”. The race  42   d  is formed with a pointed tip  58  at the center thereof. The pointed tip center  58  is formed by extending the wall of the race  42   d  inwardly tangent from a point at an angle “α” from the lowest point of the track. Similarly, the wall of the race  42   d  is extended outwardly tangent from a point at an angle “α” from the lowest point of the track. 
     There is shown in the FIG. 13 a fifth alternate embodiment of the present invention wherein similar parts are identified with the reference numerals used in the FIG. 8 and a suffix “e”. The body  41   e  has a relatively uniform thickness “C” and the body  46   e  has a relatively uniform thickness “D” with the thickness “D” being substantially larger than the thickness “C”. The race  42   c  is formed with a pointed tip  59  at the center thereof. The pointed tip center  59  is formed by extending the wall of the race  42   e  inwardly tangent from a point at an angle “α” from the lowest point of the track. The race  42   e  is substantially identical in shape to the race  42   c  shown in the FIG. 11 for receiving the ball  56 . The race  47   e  is formed with a pointed tip  60  at the center thereof. The pointed tip  60  is formed by extending the wall of the race  47   e  inwardly tangent from a point at an angle “β” from the lowest point of the track. The angles “α” and “β” can be the same or different. 
     There is shown in the FIG. 14 a sixth alternate embodiment of the present invention wherein similar parts are identified with the reference numerals used in the FIG. 8 and a suffix “f”. The race  42   f  is substantially identical in shape to the race  42   d  shown in the FIG. 12 with a pointed tip  61  in the center thereof. The body  41   f  has a relatively uniform thickness “C” and the body  46   f  has a relatively uniform thickness “D” with the thickness “D” being substantially larger than the thickness “C”. The race  47   f  is formed with a pointed tip  62  at the center thereof. The pointed tip center  62  is formed by extending the wall of the race  47   f  inwardly tangent from a point at an angle “β” from the lowest point of the track. Similarly, the wall of the race  47   f  is extended outwardly tangent from a point at an angle “β” from the lowest point of the track. 
     The various race configurations shown in the FIGS. 8-14 can be mixed and matched as desired. Further, the body  41  of the stationary bearing ring  40  could be formed thicker than or the same thickness as the body  46  of the swivel bearing ring  45 . 
     In accordance with the provisions of the patent statutes, the present invention has been described in what is considered to represent its preferred embodiment. However, it should be noted that the invention can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.