Abstract:
A zero distortion bearing pulley including a bearing is provided. The bearing clamps axially on the outer bearing raceway instead of radially. The pulley includes a stamped pulley body having a central axis, a pulley face having a periphery, a belt running surface extending perpendicularly from the periphery of the pulley face, a bearing slip pocket formed in the face coaxially with the axis of the pulley body, and a plurality of slots formed between the bearing pocket and the periphery of the pulley face. The slip pocket has a rear stop for retaining the bearing. A disc-shaped, stamped bearing retainer is provided having tabs that fit into the slots in the pulley body. The tabs may be folded over. Optionally, the tabs may have close-ended slots that allow attachment of the stamped retainer bearing to the pulley body face by rotation following insertion of the tabs into the slots.

Description:
TECHNICAL FIELD 
       [0001]    The disclosed inventive concept relates generally to pulley systems for vehicle engines. More particularly, the disclosed inventive concept relates to two-piece pulleys having ball bearings which demonstrate zero distortion of the outer bearing raceway upon assembly. 
       BACKGROUND OF THE INVENTION 
       [0002]    The modern internal combustion engine usually incorporates a pulley drive system for powering accessories driven by the engine crankshaft. The accessories typically include an air conditioning compressor, a power steering pump, a water pump, and an alternator. A front end accessory drive belt is trained around pulleys to supply power from the crankshaft of the engine to the accessories. The drive belt makes frictional contact with the face of the pulleys. The drive belt is most often a flexible reinforced polymeric belt. 
         [0003]    Each of the accessories requires a driven pulley. In addition, operating a number of accessories, particularly with a serpentine drive belt, requires that the belt be handled carefully to allow placement of the belt in the locations needed to drive the accessories without slippage. Precise location of the belt frequently calls for the use of one or more idler pulleys. 
         [0004]    The use of idler pulleys to displace the drive belt thereby allowing non-direct belt routing has demonstrated certain deficiencies. Known pulley designs incorporate ball bearings (or a cartridge type of bearing) that require a press-fit of the ball bearing assembly or over-molding of the ball bearing in the pulley body to achieve bearing retention. However, frequently the press-fitting or over-molding operation distorts the outer race of the ball bearing, resulting in irregular internal radial clearance of the bearing. The distorted outer race is known to be a contributor to NVH issues and reduces bearing durability. 
         [0005]    Another undesirable result of the assembly process is that the average radial internal clearance of the bearing is changed during press fit or over-molding operations. As a consequence, the resulting radial internal clearance tolerance of the bearing cannot be controlled tightly after press fitting or over-molding. 
         [0006]    As in so many areas of vehicle technology there is always room for improvements related to the design of a pulley for use in an internal combustion engine. Particularly, it would be advantageous to tightly control the radial internal clearance of the bearing so that bearing durability can be maximized. 
       SUMMARY OF THE INVENTION 
       [0007]    The disclosed invention overcomes the problems of known pulley designs by providing a zero distortion bearing pulley that includes a bearing. Particularly, the disclosed inventive concept includes a two-piece pulley design that clamps axially on the outer bearing raceway instead of radially. Axial retention of the bearing in the pulley affects neither the roundness of the bearing outer race nor the radial internal clearance of the bearing. 
         [0008]    The pulley includes a stamped pulley body having a central axis, a pulley face having a periphery, a belt running surface extending perpendicularly from the periphery of the pulley face, a slip pocket for a bearing formed in the face coaxially with the axis of the pulley body, and a plurality of slots formed between the bearing pocket and the periphery of the pulley face. The slip pocket has a rear stop for retaining a bearing which is fitted within the slip pocket. 
         [0009]    A disc-shaped, stamped bearing retainer is provided that has a raised rounded area of the same diameter as the outer raceway of the bearing. The bearing retainer has tabs that fit into the slots in the pulley body. The tabs may be folded over following insertion into the slots. Optionally, the tabs may have close-ended slots formed therein that allow attachment of the stamped retainer bearing to the pulley body face by rotation following insertion of the tabs into the slots. Following attachment, these tabs may also be folded over. 
         [0010]    With the front bearing retainer in place, the ball bearing is clamped to the pulley assembly axially at the outer raceway causing it to rotate when the pulley is rotated. According to the disclosed design, axial retention of the bearing in the pulley rather than radial retention results in no effect on ball bearing outer race roundness or on bearing radial internal clearance. This design also provides a continuous (one piece) belt running surface unlike other two-piece pulley designs which split the running surface between the two pieces of the pulley. 
         [0011]    The above advantages and other advantages and features will be readily apparent from the following detailed description of the preferred embodiments when taken in connection with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    For a more complete understanding of this invention, reference should now be made to the embodiments illustrated in greater detail in the accompanying drawings and described below by way of examples of the invention wherein: 
           [0013]      FIG. 1  is a sectional view of pulley according to existing technology; 
           [0014]      FIG. 2  illustrates a front view of a the zero distortion bearing pulley according to the disclosed inventive embodiment; 
           [0015]      FIG. 3  illustrates a perspective view of the zero distortion bearing pulley shown in  FIG. 1 ; 
           [0016]      FIG. 4  illustrates a perspective view of a first embodiment of a bearing retainer for use with the zero distortion bearing pulley according to the disclosed inventive concept; 
           [0017]      FIG. 5  illustrates a perspective view of a second embodiment of a bearing retainer for use with the zero distortion bearing pulley according to the disclosed inventive concept; 
           [0018]      FIG. 6  is a sectional view of the zero distortion bearing pulley according to the disclosed inventive concept upon initial fitting of the first embodiment of the bearing retainer against the bearing face in which the retainer has a flat inner surface; 
           [0019]      FIG. 7  is a sectional view of the zero distortion bearing pulley according to the disclosed inventive concept upon final fitting of the bearing retainer of  FIG. 6 ; 
           [0020]      FIG. 8  is a sectional view of the zero distortion bearing pulley according to the disclosed inventive concept upon initial fitting of the first embodiment of the bearing retainer against the bearing face in which the retainer has a raised inner surface; and 
           [0021]      FIG. 9  is a sectional view of the zero distortion bearing pulley according to the disclosed inventive concept upon final fitting of the bearing retainer of  FIG. 8 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0022]    In the following figures, the same reference numerals will be used to refer to the same components. In the following description, various operating parameters and components are described for different constructed embodiments. These specific parameters and components are included as examples and are not meant to be limiting. 
         [0023]    In general, the disclosed inventive concept provides a two-piece pulley design that clamps axially on the outer bearing raceway instead of radially resulting in axial retention of the bearing in the pulley rather than radial retention. Accordingly, the design as illustrated and discussed overcomes the problems typically associated with known pulley configurations. 
         [0024]    A pulley according to the prior art is illustrated in  FIG. 1 . As shown and understood, the assembly of parts according known pulley designs either by press-fitting or over-molding frequently results in distortion of the outer race of the ball bearing, resulting in irregular internal radial clearance of the bearing which, as noted above, contributes to NVH issues and reduces overall bearing durability. 
         [0025]    Referring to  FIG. 1 , a sectional view of pulley according to existing technology is illustrated. The pulley, generally illustrated as  10 , includes a first half  12  and a second half  14 . The halves  12  and  14  are conventionally attached by, for example, fasteners  16  and  16 ′. With the two halves  12  and  14  attached to one another, a pulley surface  18  is defined between a peripheral wall  20  formed on the first half  12  and a peripheral wall  20 ′ formed on the second half  14 . A central bore  22  is formed through the assembled halves  12  and  14  and a bearing pocket  24  is formed therebetween. A bearing  26  is fitted, typically by press-fitting, within the bearing pocket  24 . 
         [0026]    The disclosed inventive concept provides a desirable alternative to the arrangement shown in  FIG. 1  and described in relation thereto. Particularly, the design of the disclosed inventive concept provides a continuous (one piece) belt running surface unlike other two-piece pulley designs which split the running surface between the two pieces of the pulley as is illustrated on the pulley surface  18  shown in  FIG. 1 . The disclosed inventive concept is shown in  FIGS. 2 through 7  and is described hereafter. 
         [0027]    Referring to  FIGS. 2 and 3 , a front view and a perspective view are shown respectively of the zero distortion bearing pulley according to the disclosed inventive embodiment, generally illustrated as  30 . It is to be understood that the particular shape and size of the pulley  30  as shown in the figures is only suggestive and is not intended to be limiting. For example, the width of the pulley  30  as well as its diameter could be varied. 
         [0028]    The pulley  30  preferably but not absolutely formed from a stamping includes a pulley face  32  having a periphery. A pulley surface  34  extends perpendicularly from the periphery of the pulley face  32 . The pulley surface  34  is integrally formed with the pulley face  32 . A central bore  36  is formed through the pulley face  32 . Within the central bore  36  is formed a slip fit bearing pocket  38 . As is understood, the shape of the slip fit bearing pocket  38  may be varied as needed to accommodate a variety of types and sizes of bearings. A back wall  40  is formed at the inner end of the slip fit bearing pocket  38  against which the bearing is braced. 
         [0029]    Slots  42  are formed in the face  32  of the pulley  30 . The slots  42  are positioned concentric with the central bore  36  and are formed between the slip fit bearing pocket  38  and the periphery of the pulley face  32 . Tab hook receiving holes  44  are also formed on the face  32  of the pulley  30  for use with one embodiment of the bearing retainer as discussed below. The holes  44  are also positioned concentric with the central bore  36  and are formed between the slip fit bearing pocket  38  and the periphery of the pulley face  32 . 
         [0030]    A bearing assembly  46  is slip fitted into the slip fit bearing pocket  38 . The illustrated bearing assembly  46  is of the radial ball bearing type, but it is to be understood that other bearing types, including but not limited to other ball bearing types, including angular contact and deep groove ball bearings and may further include without limitation roller bearing types, such as spherical, thrust, needle and tapered roller bearings. Thus the disclosed inventive concept may be readily adapted for use in virtually any application where a pulley is needed. 
         [0031]    The pulley  30  includes a bearing retainer to hold the bearing assembly  46  in position within the slip fit bearing pocket  38 .  FIGS. 4 and 5  illustrate two embodiments of the bearing retainer according to the disclosed inventive concept. 
         [0032]    Referring to  FIG. 4 , a first embodiment of a bearing retainer according to the disclosed inventive concept is illustrated. As shown, a disc-shaped bearing retainer  50  includes a central bore  52  defined by a flat retainer wall  54 . The retainer wall  54  may alternatively have a raised rounded area as illustrated in  FIGS. 8 and 9  and as discussed in relation thereto. Adjustment and alignment holes  56  are also formed on the bearing retainer  50  for use with an assembly tool as may be needed for proper fitting. 
         [0033]    The bearing retainer  50  includes an outer periphery  58  from which a plurality of attachment tabs  60  extend. A greater or lesser number of attachment tabs  60  may be used. In addition, the attachment tabs  60  may be of shapes other than those illustrated in  FIG. 4 . 
         [0034]    Referring to  FIG. 5 , a second embodiment of a bearing retainer according to the disclosed inventive concept is illustrated. As shown, a disc-shaped bearing retainer  70  includes a central bore  72  defined by a flat retainer wall  74 . Like the retainer wall  54 , the retainer wall  74  may alternatively have a raised rounded area as illustrated in  FIGS. 8 and 9  and as discussed in relation thereto. Adjustment and alignment holes  76  are also formed on the bearing retainer  70  for use with an assembly tool as again discussed below. 
         [0035]    The bearing retainer  70  includes an outer periphery  78  from which a plurality of attachment tabs  80  extend. A greater or lesser number of attachment tabs  80  may be used. Each of the attachment tabs  80  includes an elongated tab slot  82  and an end hook  84 . 
         [0036]    A zero distortion bearing pulley according to the disclosed inventive concept is illustrated in  FIG. 6 . The assembly is illustrated upon initial fitting of the bearing retainer  50  (or the bearing retainer  70 ) to the pulley face  32 . The same pulley is illustrated in  FIG. 7 . However, in that figure, the tabs  60  are illustrated as having been folded over to lock the bearing retainer  50  in place relative to the pulley face  32 . 
         [0037]    A bearing assembly  90  is illustrated fitted in the slip fit bearing pocket  38 . The bearing assembly  90  includes an outer raceway  92 , an inner raceway  94 , and a bearing  96  retained by any of known methods, including by a bearing cage. 
         [0038]    The two embodiments of the bearing retainer, the bearing retainer  50  and the bearing retainer  70 , are initially attached to the pulley face  32  in the same manner. Specifically, the tabs  60  of the bearing retainer  50  or the tabs  80  of the bearing retainer  70  are inserted into the slots  42  formed in the pulley face  32  until the tabs  60  or the tabs  80  extend through the slots  42  as illustrated in  FIG. 6  in which a sectional view of an assembled pulley according to the disclosed inventive concept is illustrated. If the second embodiment of the bearing retainer is used, that is, the bearing retainer  70 , then an additional step of rotating the bearing retainer  70  relative to the pulley face  32  is required so that the elongated tab slots  82  fixedly engage the slots  42  of the pulley face. Once the bearing retainer  70  is fully rotated, the end hooks  84  of each of the attachment tabs  80  are locked into the tab hook receiving holes  44  of the pulley face  32 , thereby resisting reverse rotation of the bearing retainer  70 . According to this arrangement, the folding over of the attachment tabs  80  is not necessary. 
         [0039]    Regardless of the embodiment of the bearing retainer used, an adjustment and alignment tool (not shown) may be inserted through the holes  56  (if the first embodiment of the bearing retainer  50  is used) or through the holes  76  (if the second embodiment of the bearing retainer  70  is used) and into the adjustment and alignment holes  44  formed on the face  32  of the pulley  30 . 
         [0040]    Once the bearing retainers are properly attached and aligned, the tabs  60  (if the first embodiment of the bearing retainer  50  is used) or the tabs  80  (if the second embodiment of the bearing retainer  70  is used) are then folded over as illustrated in  FIG. 7 . 
         [0041]    On assembly, the retainer wall  54  presses against the outer raceway  92  of the bearing assembly  90  is illustrated in both  FIG. 6  and  FIG. 7  as the diameter of the central bore  52  is roughly the same as the inner diameter of the outer bearing raceway  92 . Accordingly, by clamping of the retainer wall  54  against the outer raceway  92  of the bearing assembly  90  according to the disclosed inventive concept, axial retention of the bearing in the pulley affects neither the roundness of the bearing outer race nor the radial internal clearance of the bearing. 
         [0042]    The bearing retainer may be modified to include a raised rounded area. This variation is illustrated in  FIGS. 8 and 9  in which a bearing retainer  98  includes a retainer wall  99  having a raised rounded area. According to this variation, the raised rounded area of the retainer wall  99  presses against the outer raceway  92  of the bearing assembly  90  as illustrated in both  FIG. 8  and  FIG. 9 . Like the retainer wall  54  discussed above, by clamping of the retainer wall  99  against the outer raceway  92  of the bearing assembly  90 , axial retention of the bearing in the pulley affects neither the roundness of the bearing outer race nor the radial internal clearance of the bearing. 
         [0043]    An additional variation of the disclosed inventive concept is illustrated in  FIG. 9  in which the tab  60  has been folded in the direction opposite that illustrated in  FIG. 7 . Both approaches are utilized to secure the bearing retainer to effectively the pulley face. 
         [0044]    One skilled in the art will readily recognize from the above discussion, and from the accompanying drawings and claims, that various changes, modifications and variations can be made therein without departing from the true spirit and fair scope of the invention as defined by the following claims.