Abstract:
A follower mechanism movable along an axis within a bore including an alignment groove. The follower mechanism includes a bucket with a cylindrical inner surface and a cylindrical outer surface, and a yoke positioned at least partially within the bucket, the yoke including a bottom wall and two opposed sidewalls depending upwardly therefrom, each sidewall defining a shaft aperture. A shaft with first and second ends is received in the shaft apertures, and a roller follower is rotatably received on the shaft such that a portion of the roller follower extends axially outwardly beyond the bucket.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates generally to follower mechanisms. More particularly, the present invention relates to designs and assembly methods of follower mechanisms and their associated alignment devices. 
       BACKGROUND OF THE INVENTION 
       [0002]    Follower mechanisms are often used in a valve train of an internal combustion engine to transmit motion from a camshaft of the engine to one or more intake or exhaust valves. As the camshaft rotates, the follower mechanisms receive both a sideways force and a downward force from corresponding lobes on the camshaft, but only transmit the downward force to the valves to open and/or close the valves. Follower mechanisms thereby reduce the possibility of bending or otherwise damaging the valve stems of the valves. As well, follower mechanisms are often used in camshaft driven, high-pressure fuel pumps which are used in gasoline direct injection systems. 
         [0003]    Existing bucket-type follower mechanisms typically include either a stamped or cold formed bucket. A roller follower is typically supported on a shaft that is directly fixed to the bucket such as by staking, swaging, etc. As such, the bucket is a load bearing member and, therefore, requires heat treatment and operations such as grinding. As well, follower mechanisms often have some form of alignment device carried in an aperture defined by the bucket such that rotation of the follower mechanism within its corresponding bore is prevented. One example of known alignment devices includes a mushroom-shaped pin that is fixed in an aperture of the follower mechanism&#39;s bucket. Such pins can be difficult to manufacture because of their complicated shapes. As well, required heat treatments of the bucket can cause distortion of the aperture which receives the alignment device, thereby complicating assembly. Such alignment devices are often fixed in their corresponding apertures by an interference fit. 
         [0004]    The present invention recognizes and addresses considerations of prior art constructions and methods. 
       SUMMARY OF THE INVENTION 
       [0005]    One embodiment of the present disclosure provides a follower mechanism movable along an axis within a bore including an alignment groove. The follower mechanism includes a bucket with a cylindrical inner surface and a cylindrical outer surface, and a yoke positioned at least partially within the bucket, the yoke including a bottom wall and two opposed sidewalls depending upwardly therefrom, each sidewall defining a shaft aperture. A shaft with first and second ends is received in the shaft apertures, and a roller follower is rotatably received on the shaft such that a portion of the roller follower extends axially outwardly beyond the bucket. 
         [0006]    Another embodiment of the present disclosure provides a follower mechanism movable along an axis within a bore including an alignment groove. The follower mechanism includes a bucket with a cylindrical inner surface and a cylindrical outer surface, and defining an aperture, the aperture having a length parallel to the axis and a width transverse to the axis. An alignment device is positioned at least partially within the aperture, the alignment device having a length parallel to the axis and a width transverse to the axis, wherein a maximum length of the aperture is greater than a maximum length of the alignment device and a maximum width of the aperture is greater than a maximum width of the alignment device. 
         [0007]    Another embodiment of the present disclosure provides a follower mechanism movable along an axis within a bore including an alignment groove. The follower mechanism includes a bucket with a cylindrical inner surface and a cylindrical outer surface, and defining an aperture, the aperture having a length parallel to the axis and a width transverse to the axis. An alignment device is positioned at least partially within the aperture, the alignment device having a length parallel to the axis and a width transverse to the axis. The alignment device has a generally rectangular cross-sectional shape when taken through a plane in which both a longitudinal center axis of the alignment device and the axis of the bore lie. 
         [0008]    The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate one or more embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended drawings, in which; 
           [0010]      FIG. 1  is a perspective view of an embodiment of a follower mechanism including an alignment device in accordance with the present disclosure; 
           [0011]      FIG. 2  is a top view of the follower mechanism shown in  FIG. 1 ; 
           [0012]      FIG. 3  is an exploded perspective view of the follower mechanism shown in  FIG. 1 ; 
           [0013]      FIG. 4  is a top view of a bucket of the follower mechanism shown in  FIG. 1 ; 
           [0014]      FIGS. 5A and 5B  are perspective and top views, respectively, of a yoke of the follower mechanism shown in  FIG. 1 ; 
           [0015]      FIG. 6A  is a partial cross-sectional view of the follower mechanism and alignment device, taken along line  6 A- 6 A of  FIG. 1 ; 
           [0016]      FIG. 6B  is a partial cross-sectional view of an alternate embodiment of a follower mechanism in accordance with the present disclosure; 
           [0017]      FIG. 7  is a partial cross-sectional view of an alternate embodiment of a follower mechanism in accordance with the present disclosure; 
           [0018]      FIG. 8  is a partial cross-sectional view of an alternate embodiment of a follower mechanism in accordance with the present disclosure; 
           [0019]      FIG. 9  is a partial cross-section view of an alternate embodiment of a follower mechanism in accordance with the present disclosure; 
           [0020]      FIGS. 10A and 10B  are a perspective and a top view, respectively, of an alternate embodiment of a follower mechanism and alignment device in accordance with the present disclosure; 
           [0021]      FIGS. 11A and 11B  are a perspective view and a top view, respectively, of an alternate embodiment of a follower mechanism and alignment device in accordance with the present disclosure; 
           [0022]      FIG. 12  is a perspective cross-sectional view of the follower mechanism shown in  FIGS. 11A and 11B ; and 
           [0023]      FIG. 13  is a partial cross-sectional view of the follower mechanism and alignment device shown in  FIG. 1  assembled in a cylinder head. 
       
    
    
       [0024]    Repeat use of reference characters in the present specification and drawings is intended to represent same or analogous features or elements of the invention according to the disclosure. 
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0025]    Reference will now be made in detail to presently preferred embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. Each example is provided by way of explanation, not limitation, of the invention. In fact, it will be apparent to those skilled in the art that modifications and variations can be made in the present invention without departing from the scope and spirit thereof. For instance, features illustrated or described as part of one embodiment may be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents. 
         [0026]    Referring now to the figures, as shown in  FIGS. 1 through 3 , an embodiment of a follower mechanism  10  in accordance with the present disclosure includes a substantially cylindrical bucket  20 , a yoke  40  received therein, a roller follower  60  supported by yoke  40 , and an alignment device  70  received in an aperture  26  of bucket  20 . As shown in  FIG. 13 , follower mechanism  10  is configured for use in a valve train of an internal combustion engine to facilitate opening and closing an intake valve or an exhaust valve of the valve train. As a camshaft  19  of the engine rotates, a lobe  18  of camshaft  19 , or a rocker arm (not shown) connected to camshaft  19 , engages roller follower  60  of follower mechanism  10  to convert the rotational motion of camshaft  19  into linear motion of follower mechanism  10  within a bore  12  of a corresponding cylinder head  14 . A valve stem  90  of valve  92  is positioned within and connected to follower mechanism  10  such that, as follower mechanism  10  moves in a linear direction within bore  14 , valve  92  is alternatingly opened and closed. Forces from camshaft  19  are thereby transmitted through follower mechanism  10  to valve  92  such that only forces in substantially the same direction as the motion of valve  92  act on valve  92 . In addition, follower mechanism  10  serves as a torsional vibration isolation device between camshaft  19  and valve  92  to inhibit rotational forces from being transmitted to valve  92 . As shown, alignment device  70  is a substantially cylindrical rod, a portion of which is slidably received in a correspondingly shaped alignment groove  16  defined by the inner wall of bore  12 . 
         [0027]    Referring additionally to  FIG. 4 , bucket  20  of the present embodiment includes a cylindrical outer surface  22 , a cylindrical inner surface  24  substantially concentric therewith, and aperture  26  defined therein for receiving alignment device  70 . As shown, aperture  26  is generally rectangular and is formed by a pair of opposed sidewalls  28 , a top wall  30 , and a bottom wall  32 . Opposed side walls  28  are substantially parallel to each other, as are top wall  30  and bottom wall  32 , which in addition, are substantially transverse to opposed side walls  28 . As discussed in greater detail below, although aperture  26  is greater in height than alignment device  70  to facilitate insertion, aperture  26  is more narrow in width than alignment device  70  such that alignment device  70  is received in aperture  26  by a press-fit. In an alternate embodiment, the aperture is generally larger, both wider and higher, than alignment device  70  to provide clearance for alignment device  70  during assembly. Bucket  20  can be formed by a stamping process, in which case aperture is formed by, for example, piercing, machining, or otherwise cutting into bucket  20 . Alternately, bucket  20  can be formed by a powdered metal process. 
         [0028]    Bucket  20  also includes a plurality of axially extending grooves  34  defined by inner surface  24 . Each axially extending groove  34  extends downwardly from a top edge of bucket  20  and terminates at a corresponding stop face  36  such that axially extending grooves  34  extend along only a portion of the height of bucket  20 . Each axially extending groove  34  is configured to slidably receive a corresponding corner  52  of a bottom wall  42  of yoke  40  such that yoke  40  is slidably received within bucket  20 . Axially extending grooves  34  can be formed by a broaching process where bucket  20  is formed by stamping, or may be formed by a process using powdered metal. 
         [0029]    Referring additionally to  FIGS. 5A and 5B , yoke  40  includes bottom wall  42 , a pair of opposed sidewalls  44  extending upwardly therefrom, a pair of shaft apertures  48  defined by sidewalls  44 , and a projection  46  extending outwardly from a peripheral edge of bottom wall  42 . As shown, bottom wall  42  is substantially rectangular with sidewalls  44  extending upwardly from a pair of its opposed edges. Each corner  52  of bottom wall  42  is slidably received in a corresponding axially extending groove  34  of bucket  20  until corners  52  of bottom wall  42  abut corresponding stop faces  36 . As shown in  FIGS. 1 and 13 , when fully inserted in bucket  20 , the uppermost ends of the yoke&#39;s sidewalls  44  extend axially outwardly beyond the top edge of bucket  20 . Additionally, once fully inserted in bucket  20 , yoke  40  is retained therein by staking, swaging, welding, etc. Preferably, yoke  40  is formed by a stamping process and is subjected to heat treatment processes as well. Projection  46  includes an abutment surface  50  at its distal end that is correspondingly shaped to a portion of an outer surface  72  of alignment device  70 . Axially extending grooves  34  of bucket  20  are configured such that when yoke  40  is fully inserted in bucket  20 , abutment surface  50  of projection  46  is positioned radially inwardly of aperture  26  so that it may receive alignment device  70  ( FIG. 6 ). 
         [0030]    As best seen in  FIG. 3 , roller follower  60  includes shaft  62 , an outer race  66 , and a plurality of rollers  64  disposed therebetween such that race  66  is freely rotatable about shaft  62 . Opposite ends of shaft  62  are received in shaft apertures  48  of yoke  40  such that roller follower  60  is mounted to bucket  20  of follower mechanism  10 . When assembled, roller follower  60  extends axially outwardly beyond the top edge of bucket  20  such that outer surface  68  of race  66  engages a corresponding lobe  18  of camshaft  19 , as shown in  FIG. 12 . Preferably, the diameters of shaft apertures  48  are slightly larger than the diameter of shaft  62  such that shaft  62  is free to precess within shaft apertures  48  during operation. Alternately, the opposing ends of shaft  62  can be staked, swaged, etc., to yoke  40  such that rotation relative thereto is prevented. 
         [0031]    As previously noted, alignment device  70  is a substantially cylindrical rod including cylindrical outer surface  72  and substantially parallel top and bottom surfaces  74  and  76 , respectively. As best seen in  FIG. 6A , a width X defined by sidewalls  28  of aperture  26  is slightly less than the diameter of cylindrical rod  70 . Preferably, cylindrical rod  70  is positioned in aperture  26  from the outside of bucket  20  in a press fit subsequent to assembly of yoke  40  and roller follower  60  within bucket  20 . As such, cylindrical rod  70  is retained in aperture  26  once assembled. The height defined by top wall  30  and bottom wall  32  of aperture  26  is greater than the height of cylindrical rod  70  as defined by top surface  74  and bottom surface  76  to facilitate insertion of cylindrical rod  70  into aperture  26 . When fully assembled in bucket  20 , abutment surface  50  of projection  46  supports cylindrical rod  70  such that a portion of cylindrical rod  70  extends radially outwardly beyond outer surface  22  of bucket  20 , and is therefore slidably received in alignment groove  16  of bore  12 . 
         [0032]    Referring now to  FIG. 6B , an alternate embodiment of an alignment device in accordance with the present disclosure is shown. As best seen in  FIG. 6B , a width X defined by sidewalls  28  of aperture  26  is greater than the diameter of cylindrical rod  70 . Additionally, the height defined by top wall  30  and bottom wall  32  of aperture  26  is greater than the height of cylindrical rod  70  as defined by top surface  74  and bottom surface  76 . As such, cylindrical rod  70  can be positioned in aperture  26  from the outside of bucket  20  subsequent to assembly of yoke  40  and roller follower  60  within bucket  20 . When fully assembled in bucket  20 , abutment surface  50  of projection  46  receives cylindrical rod  70  such that a portion of cylindrical rod  70  extends radially outwardly beyond outer surface  22  of bucket  20 , and is therefore slidably received in alignment groove  16  of bore  12 . 
         [0033]    Referring now to  FIG. 7 , an alternate embodiment of an alignment device in accordance with the present disclosure is shown. The alignment device includes a cylindrical rod  70  as previously discussed. However, an aperture  26   a  defined in bucket  20  differs from the aperture of the previously discussed embodiment. More specifically, although the height of aperture  26   a  is slightly greater than the height of cylindrical rod  70 , and a width X of aperture  26   a  at inner surface  24  is slightly greater than a diameter of cylindrical rod  70 , a width Y of aperture  26   a  at outer surface  22  is less than the diameter of cylindrical rod  70 . Therefore, cylindrical rod  70  cannot be inserted into aperture  26   a  from the outside of bucket  20 . As such, cylindrical rod  70  is inserted in aperture  26   a  from the inside of bucket  20  prior to assembly of yoke  40  and roller follower  60  within bucket  20 . Note, opposed sidewalls  28   a  of aperture  26   a  are not substantially parallel in that their outermost edges are closer together than their innermost edges. Note, for the embodiment shown in  FIGS. 6A ,  6 B and  7 , cylindrical rod  70  can be replaced with a round bearing if apertures  26  and  26   a , respectively, are circular rather that rectangular. 
         [0034]    Referring now to  FIG. 8 , an alternate embodiment of an alignment device in accordance with the present disclosure is shown. The alignment device is substantially similar to the alignment device as shown in  FIGS. 1 through 6 , with only those elements that differ receiving alternate reference numerals. As shown, the alignment device is a rectangular rod that is received in aperture  26  defined by bucket  20 . In that rectangular rod  70   a  includes four substantially planar sides defining its outer surface, abutment surface  50   a  of the yoke&#39;s projection  46   a  is formed by a planar surface for receiving rectangular rod  70   a . As shown, the portion of rectangular rod  70   a  that extends outwardly beyond outer surface  22  of bucket  20  is substantially rectangular in shape. As such, the corresponding alignment groove (not shown) defined by bore  12  in which follower mechanism  10  is slidably received has a correspondingly-shaped cross section. 
         [0035]    Referring now to  FIG. 9 , an alternate embodiment of an alignment device in accordance with the present disclosure is shown. The alignment device is substantially similar to the alignment device as shown in  FIGS. 1 through 6 , with only those elements that differ receiving alternate reference numerals. As shown, the alignment device includes a rectangular portion that is received in aperture  26  of bucket  20  and a curved portion that extends radially outward from outer surface  22  of bucket  20 . In that rod  70   b  includes a substantially planar side defining its innermost surface, abutment surface  50   a  of the yoke&#39;s projection  46   a  is formed by a planar surface for receiving rod  70   b . As noted, the portion of rod  70   b  that extends outwardly beyond outer surface  22  of bucket  20  is curved in shape. As such, the corresponding alignment groove  16  ( FIG. 13 ) defined by bore  12  in which follower mechanism  10  is slidably received has a correspondingly-shaped cross section. 
         [0036]    Referring now to  FIGS. 10A and 10B , a follower mechanism  10   c  including an alternate embodiment of an alignment device in accordance with the present disclosure is shown. Follower mechanism  10   c  differs primarily from the first embodiment as discussed with regard to  FIGS. 1 through 6  in that bucket  20   c  of follower mechanism  10   c  is formed by a process using powdered metal. By forming bucket  20   c  with powdered metal, the alignment device may be formed as an integral projection  70   c  of bucket  20   c . As such, a separate alignment device is not required and there is no need to form an aperture for receiving an alignment device in bucket  20   c . Additionally, yoke  40  is not required to have a projection  46  as in the previously discussed embodiments. 
         [0037]    Referring now to  FIGS. 11A and 11B , an alternate embodiment of a follower mechanism  10   d  in accordance with the present disclosure is shown. Follower mechanism  10   d  differs primarily from the embodiment as discussed with regard to  FIGS. 10A and 10B  in that bucket  20   d  of follower mechanism  10   d  includes a pair of yoke supports  25 , each of which extends radially inwardly into the interior of bucket  20   d . Each yoke support  25  defines an axially extending groove  34   d  that extends downwardly from a tope edge of bucket  20   d  and terminates at a corresponding stop face  36   d . As such, each axially extending groove  34   d  extends along only a portion of the height of bucket  20   d . Each axially extending groove  34   d  is configured to slidably receive a corresponding side wall  44  of yoke  40  such that yoke  40  is slidably received within bucket  20   d . Similar to the embodiment shown in  FIGS. 10A and 10B , bucket  20   d  is formed with a powdered metal such that the alignment device may be formed as an integral projection  70   d  of bucket  20   d.    
         [0038]    Although the preceding embodiments of follower mechanisms have been described for use in an internal combustion engine, they may be used in alternate types of assemblies where it is desirable to translate rotational motion of one component into linear motion of another component. For example, they may be configured for use in a fluid pump to help drive a fluid (e.g., fuel, oil, water, or the like). More specifically, they may be used in camshaft driven high-pressure fuel pumps as used in gasoline direct injection systems. 
         [0039]    While one or more preferred embodiments of the invention are described above, it should be appreciated by those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope and spirit thereof. For example, the cross-sectional shapes of the alignment devices and corresponding grooves may be of any shape found to be suitable for the intended purpose. Additionally, the vibration isolator may be constructed of any material found to be suitable for the intended purpose. It is intended that the present invention cover such modifications and variations as come within the scope and spirit of the appended claims and their equivalents.