Abstract:
An object is to provide a retainer for a thrust bearing, from which rollers are not apt to drop once placed in pockets in the retainer in a manufacturing processes. A retainer is constituted by an annular member made from a flat steel plate; has a main body area in its widthwise intermediate region. The main body area has its outer circumferential edge formed with an outer circumferential engagement edge which is lower than a surface of the main body area. A large number of pockets are equi-spaced in a circumferential direction of the main body area in the thickness direction. Each of the pockets has a guide surface formed with anti-dropping projections of a roller for preventing the roller from dropping.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a retainer for a thrust bearing, and a thrust bearing which uses the retainer. 
       BACKGROUND ART 
       [0002]    Thrust bearings used in automobile transmissions or torque converters sometimes must be designed to have very short rollers due to very limited surface areas for the rollers to roll on a paired part. 
         [0003]    Short rollers have a problem that their attitude is unstable in pockets in a retainer, and that rollers are more apt to drop from the pockets during manufacture (Patent Literature 1; see  FIG. 2 ). 
         [0004]    In order to prevent rollers from dropping, it is necessary to increase the depth of the pockets in the retainer, and to capture each of the rollers on its outer diameter surface at two locations which are radially as apart as possible from the center of the roller. Such a retainer has already known: It includes two retainer members each formed with grooves in an annular pattern; the two members are axially assembled with each other with the grooves opposed to each other to provide hollow spaces in an annular pattern; pockets which axially penetrates the space for holding the rollers are provided (Patent Literature 2). 
         [0005]    However, this retainer requires some arrangement in order to prevent the two retainer members from being separated from each other. For example, it is necessary to provide knurling on the annular groove areas to make rough surfaces. 
         [0006]    There are also known other retainers for thrust bearings: One example includes an annular metal plate each having its widthwise intermediate region formed with stepped bents arranged circumferentially all around the plate; and another example is to form generally S-shaped bents (Patent Literature 3). A problem in this type of retainers is a relatively thin plate thickness, which results in shallow pockets and therefore a narrow radial distance between anti-drop nails. In other words, short rollers (those having a short length) are apt to drop. 
         [0007]    Still another example is a so-called trinity type thrust bearing in which an outer ring, an inner ring and a retainer between these are non-separable. In this type of thrust bearing, the outer ring has bent nails, or engagement margins are formed by means of staking. In this arrangement, resin retainers are subject to grinding wear, so resin retainers cannot be used in the trinity type. 
       CITATION LIST 
     Patent Literature 
       [0008]    Patent Literature 1: Japanese Patent No. 3661133 Gazette 
         [0009]    Patent Literature 2: Japanese Patent No. 3900843 Gazette 
         [0010]    Patent Literature 3: JP-A H11-336751 Gazette 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0011]    In consideration to the conventional techniques as described above, it is an object of the present invention to provide a retainer from which rollers are not apt to drop once placed in pockets in the retainer in manufacturing processes; and to provide a thrust bearing using the retainer. 
       Solution to Problem 
       [0012]    In order to solve the above-mentioned problems, the present invention provides a retainer for a thrust bearing, which includes an annular member formed with a large number of pockets at an interval in a circumferential direction for holding rollers, wherein the annular member is made of a flat steel plate; has a main body area of a constant thickness in its widthwise intermediate region; the main body area has its outer circumferential edge formed with an outer circumferential engagement edge having a surface lower than that of the main body area; the pockets are equi-spaced in a circumferential direction of the main body area and are provided by through-holes in a thickness direction; and each pocket has its guide surfaces formed with anti-dropping projections for preventing a roller from dropping. 
         [0013]    In cases where an outer ring is used in combination with the retainer which holds rollers, the outer ring has engaging hooks for engagement with the outer circumferential engagement edge to non-separatingly assemble the two components with each other. 
         [0014]    In cases where an inner ring is added to the example described above, the retainer has an inner circumferential edge on a surface away from a surface formed with the outer circumferential engagement edge, and the inner circumferential edge is formed with an inner circumferential engagement edge which recedes from said surface. The inner ring is formed with engaging hooks for engagement with the inner circumferential engagement edge to non-separatingly assemble the three components together. 
         [0015]    The retainer&#39;s main body area is has a thickness which is 0.5 through 0.9 times of a diameter of the rollers. This makes the pockets, which penetrate the main body area, deep enough to cover the rollers, thereby stabilizing the rollers&#39; attitude and make them less apt to drop from the pockets. 
         [0016]    Further, the anti-dropping projections for preventing the roller from dropping, at both axial end areas in both of the guide surfaces in a circumferential direction of the retainer of the pockets, ensure more reliable prevention of the rollers from dropping. 
       Advantageous Effects of Invention 
       [0017]    As described, the retainer according to the present invention is made of a flat annular steel plate; has pockets in a main body area of a constant thickness in its widthwise intermediate region. The arrangement ensures to provide a sufficient depth in the pocket, and therefore, even if the rollers are short, the rollers keep stable attitudes. Also, anti-dropping projections formed in each pocket, at both axial end areas in guide surfaces across the retainer&#39;s circumferential direction, reliably prevent the rollers from dropping out of the retainer in manufacturing processes. 
         [0018]    Also, the retainer has an outer circumferential engagement edge or an inner circumferential engagement edge for engagement with the outer ring or with the inner ring. This provides a non-separating assembly of the two or the three components. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0019]      FIG. 1  is a plan view of a thrust bearing according to Embodiment 1. 
           [0020]      FIG. 2  is a sectional view taken in lines X 1 -X 1  in  FIG. 1 . 
           [0021]      FIG. 3  is an enlarged sectional view of a portion taken from  FIG. 1 . 
           [0022]      FIG. 4  is a perspective view of the retainer, showing its sections. 
           [0023]      FIG. 5  is an enlarged sectional view taken in lines X 2 -X 2  in  FIG. 4 . 
           [0024]      FIG. 6  is a perspective view of another retainer, showing its sections. 
           [0025]      FIG. 7  is an enlarged sectional view taken in lines X 3 -X 3  in  FIG. 6 . 
           [0026]      FIG. 8  is a perspective view of another retainer, showing its sections. 
           [0027]      FIG. 9  is an enlarged sectional view taken in lines X 4 -X 4  in  FIG. 8 . 
           [0028]      FIG. 10  is a perspective view of another retainer, showing its sections. 
           [0029]      FIG. 11  is an enlarged sectional view taken in lines X 5 -X 5  in  FIG. 10 . 
           [0030]      FIG. 12  is a plan view of a thrust bearing according to Embodiment 2. 
           [0031]      FIG. 13  is a partially unillustrated enlarged sectional view taken in lines X 6 -X 6  in  FIG. 12 . 
           [0032]      FIG. 14  is an enlarged partial plan view of a portion in  FIG. 12 . 
           [0033]      FIG. 15  is a partially unillustrated sectional view of a thrust bearing according to Embodiment 3. 
           [0034]      FIG. 16  is a partially unillustrated enlarged sectional view of a thrust bearing according to Embodiment 4. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0035]    Hereinafter, embodiments of the present invention will be described based on the attached drawings. 
       Embodiment 1 
       [0036]      FIG. 1  through  FIG. 5  show a thrust bearing according to Embodiment 1, which includes an outer ring  11 , an inner ring  12 , a predetermined number of rollers  13  between these two members, and a retainer  14  which holds the rollers  13 . 
         [0037]    The retainer  14  is formed of a flat annular member  15  (see  FIG. 4 ) which is made by punching a steel plate. The annular member  15  has a main body area  16  of a constant thickness, in its widthwise intermediate region. The main body area  16  has its outer circumferential edge region formed with a stepped area  17 , which is surrounded by a thin, outer circumferential engagement edge  18 . On a surface which is away from the one formed with the outer circumferential engagement edge  18 , there is formed there is formed a thin, inner circumferential engagement edge  20  along its inner circumferential edge via a stepped area  19 . 
         [0038]    The outer circumferential engagement edge  18  and the inner circumferential engagement edge  20  can be formed by various kinds of machining processes such as pressing, coining, crushing, etc. In the embodiment shown in the figures, the outer circumferential engagement edge  18  has a greater width than the inner circumferential engagement edge  20 . 
         [0039]    The main body area  16  described above has a thickness which is 0.5 through 0.9 times the diameter of the rollers  13 . As shown in  FIG. 3 , slight gaps x 1 , x 2  will develop during the use, between a track surface  21  of the outer ring  11  and the main body area  16 , as well as between a track surface  22  of the inner ring  12  and the main body area  16 , respectively. The main body area  16  has received no such machining processes as pressing, so the main body area  16  has a uniform thickness along its entire circumference and the steel material in this area has a uniform fiber flow. 
         [0040]    As shown in  FIG. 4  and  FIG. 5 , the main body area  16  is formed with a large number of rectangular pockets  23  at a constant interval along an entire circumference. Each pocket  23  is provided by a through-hole in a thickness direction of the main body area  16 . The pocket  23  has two sides, each having a guide surface  24  and in both of them (i.e., in both guide surfaces  24  across the circumferential direction of the retainer  14 ), anti-dropping projections  25 ,  26  of the rollers  13  are formed at respective axial ends (see  FIG. 5 ) in order to prevent the roller from dropping. These anti-dropping projections  25 ,  26  can be formed by swaging, stamping, burnishing, or other machining operations. 
         [0041]    The outer ring  11  has an outer circumferential edge formed with an axially erected flange  27 , which has an inner circumferential surface opposed to the outer circumferential engagement edge  18  of the retainer  14 . The flange  27  is erected by a height which is slightly higher than a thickness of the outer circumferential engagement edge  18  in the retainer  14 . The flange  27  has an engaging hook  28  at its tip edge, which is inwardly bent extending over the track surface  21 , so that the bearing can have a large inner gap. 
         [0042]    The engaging hook  28  is formed at a plurality of locations along the entire circumference, so each makes axial engagement with an outer circumferential engagement edge  18  of the retainer  14  with a certain engagement margin. As a result, the outer ring  11  and the retainer  14  are non-separatingly assembled with each other. 
         [0043]    Between two mutually adjacent engaging hooks  28 , the flange  27  has its upper end edge formed with a reinforcing piece  29  to extend upward but not to exceed the inner ring  12  (see  FIG. 2 ), for reinforcement to the flange  27 . 
         [0044]    The inner ring  12  has an inner circumferential edge formed with an axially inward bending flange  31 , which has an inner circumferential surface opposed to the inner circumferential engagement edge  20  of the retainer  14 . The flange  31  has its tip edge formed with radially outward protruding engagement projections  32  at a plurality of locations along the circumferential direction. These engagement projections  32  make axial engagement with the inner circumferential engagement edge  20  of the retainer  14  with a predetermined engagement margin. As a result, the inner ring  12  and the retainer  14  are non-separatingly assembled with each other. 
         [0045]    As a variation of the above-described retainer  14 ,  FIG. 6  and  FIG. 7  show a retainer which includes a main body area having both of its surfaces formed with grooves  33  alternating with the pockets  23 . These grooves  33  decrease the weight of the retainer  14 , while serving as places for lubricant to pool.  FIG. 8  and  FIG. 9  show another example of the same intent, where a main body area  16  is formed with recesses  34  along its inner circumferential edge, alternating with the pockets  23 .  FIG. 10  and  FIG. 11  show still another example, where the pockets  23  are alternated with slit-like through-holes  35  for further weight reduction and improved flow of lubricant in the retainer  14 . 
         [0046]    The thrust bearing according to Embodiment 1 is as described thus far: The retainer  14  is made of a steel plate; has a main body area  16  of a constant thickness; and the main body area  16  is formed with pockets  23 ; so, most part of the rollers  13  are inside the pockets  23  except for very small portions (exposed to gaps x 1 , x 2 ) which make contact with the track surfaces  21 ,  22  of the outer ring  11  and the inner ring  12 . Therefore, even if the rollers are short, they keep stable attitudes. 
         [0047]    Also, the anti-dropping projections  25 ,  26  provided on both guide surfaces  24  of the pockets  23  ensure reliable prevention of the rollers  13  from dropping. 
       Embodiment 2  
       [0048]      FIG. 12  through  FIG. 14  show a thrust bearing according to Embodiment 2, which is basically identical with Embodiment 1, but as has been mentioned already, the outer circumferential engagement edge  18  in the retainer  14  according to Embodiment 2 has the same width as the width of the inner circumferential engagement edge  20 , for applications where internal space in the bearing is relatively small. For this reason, engaging hooks  28   a  formed at the tip edge of the flange  27  in the outer ring  11  do not have to have a long protrusion, and therefore are formed by means of staking. Other arrangements are identical with those in Embodiment 1. 
       Embodiment 3 
       [0049]      FIG. 15  shows a thrust bearing according to Embodiment 3, which is constituted by an outer ring  11 , and a retainer  14  which holds rollers  13 . This retainer  14  differs from those which have been described earlier, in that an outer circumferential engagement edge  18   a  formed on an outer circumferential edge in the main body area  16  is tapered. The outer ring  11  has a flange  27  which has its tip end edge formed with engaging hooks  28   a  by means of staking, and these engaging hooks  28   a  keep the outer ring  11  and the retainer  14  assembled with each other. 
         [0050]    It should be noted here that if an inner ring  12  is used, a tapered inner circumferential engagement edge  20   a  is formed on a surface away from the surface where the outer circumferential engagement edge  18   a,  in the main body area  16  is formed. 
       Embodiment 4 
       [0051]      FIG. 16  shows a thrust bearing according to Embodiment 4, which basically follows the arrangements used in the previous Embodiment 1 and Embodiment 2, in that an annular member  15  has a main body area  16  of a constant thickness in its widthwise intermediate region, and this main body area  16  has its outer circumferential edge region formed with a stepped area  17 , which is surrounded by a thin, outer circumferential engagement edge  18 . Also, on a surface which is away from the one formed with the outer circumferential engagement edge  18 , there is formed a thin, inner circumferential engagement edge  20  along its inner circumferential edge via a stepped area  19 . The difference, however, from the previous Embodiment 1 and Embodiment 2 is that the stepped area  17  on the outer diameter side and the stepped area  19  on the inner diameter side are extended into the pockets  23 . 
         [0052]    The arrangement that the stepped area  17  on the outer diameter side and the stepped area  19  on the inner diameter side are extended into the pockets  23  improves lubricant flow and foreign matter discharge. 
         [0053]      FIG. 16  shows a case where both the stepped area  17  on the outer diameter side and the stepped area  19  on the inner diameter side are provided beyond the pockets  23 . However, at least one of the stepped area  17  on the outer diameter side and the stepped area  19  on the inner diameter side may be provided beyond the pockets  23 . 
       REFERENCE SIGNS LIST 
       [0000]    
       
           11  outer ring 
           12  inner ring 
           13  rollers 
           14  retainer 
           15  annular member 
           16  main body area 
           17  stepped area 
           18 ,  18   a  outer circumferential engagement edge 
           19  stepped area 
           20 ,  20   a  inner circumferential engagement edge 
           21  track surface 
           22  track surface 
           23  pockets 
           24  guide surface 
           25  anti-dropping projection 
           26  anti-dropping projection 
           27  flange 
           28 ,  28   a  engaging hook 
           29  reinforcing piece 
           31  flange 
           32  engagement projection 
           33  groove 
           34  recess 
           35  through-hole