Abstract:
A finger follower having an inner and outer body and a torsional lost motion spring acting between the bodies is provided. A roller cam follower is connected to the inner body. The inner body is switchable from a fixed state, in which it moves with the outer body to transfer a cam lift to a valve stem, to a released state, in which the inner body can move relative to the outer body so that the cam lift is not transferred to the valve stem. A separate valve pallet that acts on the valve stem is press fit or otherwise rotationally fixed on a pivot pin connecting the inner and outer bodies.

Description:
INCORPORATION BY REFERENCE 
       [0001]    The following documents are incorporated herein by reference as if fully set forth: U.S. Provisional Application No. 61/589,505, filed Jan. 23, 2012. 
     
    
     FIELD OF INVENTION 
       [0002]    The invention relates to roller finger followers that are used in overhead cam type internal combustion engines and, more particularly, to switchable roller finger followers that have a lift and a no lift mode. 
       BACKGROUND 
       [0003]    Switchable roller finger followers that have at least one lift mode and a no lift mode are known. Typically, such finger followers have an outer elongated body, one end of which contacts a valve stem and operates on the valve stem, and a second end which is in contact with a hydraulic lash adjuster. The end which contacts the valve stem is formed on the outer elongated body and includes side walls to ensure that its position on the valve stem is maintained. This requires complex machining or formation of the outer elongated body. An inner elongated body is located in the outer elongated body and houses a cam follower that is contacted by the cam so as to provide motion to the finger follower to open or close the valve. The inner elongated body has two modes, a locked mode and an unlocked mode. A latching mechanism on the outer elongated body is used to lock the inner elongated body in a fixed position relative to the outer body. When the inner elongated body is locked in a stationary position, the cam which is fixed to the cam shaft of the engine translates movement to the finger follower which in turn translates into movement of the valve via the valve stem. In order to deactivate the finger follower, the latching mechanism is released and the inner elongated body is unlocked and can travel freely up and down in conjunction with the cam without transferring the cam motion to the outer body and valve stem. 
         [0004]    U.S. Pat. No. 7,909,007 discloses a roller finger follower of this type. This provides a lost motion spring to maintain contact between the cam follower and the cam. 
         [0005]    It would be desirable to provide a finger follower of the type noted above with simpler manufacturing and reduced costs. 
       SUMMARY 
       [0006]    A switchable roller finger follower is provided having an outer elongated body with a valve stem end, a lash adjuster end and two outer elongated body side walls. A first inner cavity is located in said outer elongated body. An inner elongated body is positioned in the first inner cavity and has a first end pivotally attached to the outer elongated body at the valve stem end via a pin. A second end of the inner elongated body is located adjacent to the lash adjuster end of the outer elongated body. A lost motion spring is located between the inner and outer elongated bodies. A latching mechanism is provided to lock the inner elongated body in a fixed position relative to the outer elongated body, and can be released in order to allow movement between the inner and outer elongated bodies. A valve stem pallet is located between the two outer elongated body side walls and is connected in a rotationally fixed manner to the pivot pin. The valve stem pallet can be separately manufactured via cold forming, machining, punching and/or bending up sheet metal, or by various other methods. By separately forming the valve stem pallet from the outer elongated body, manufacturing is simplified and costs are reduced. 
         [0007]    In another aspect of the invention, the motion of the valve stem pallet is limited by stops on or connected to the outer elongated body. 
         [0008]    Other aspects of the invention are described below and in the claims, and have not been repeated here. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0009]    The foregoing Summary and the following detailed description will be better understood when read in conjunction with the appended drawings, which illustrate a preferred embodiment of the invention. In the drawings: 
           [0010]      FIG. 1  is a perspective view of a finger follower in accordance with the prior art. 
           [0011]      FIG. 2  is a perspective view of a finger follower in accordance with the present invention. 
           [0012]      FIG. 3  is an enlarged perspective view of a portion of the finger follower of  FIG. 2 . 
           [0013]      FIG. 4  is a perspective view of a valve stem pallet used in connection with the finger follower of  FIGS. 2 and 3 . 
           [0014]      FIG. 5  is a perspective view of an alternate embodiment of the valve stem pallet similar to the valve stem pallet shown in  FIG. 4 . 
           [0015]      FIG. 6  is a cross-sectional view through the valve stem pallet shown in  FIG. 5  taken along line  6 - 6  in  FIG. 5 . 
           [0016]      FIG. 7  is a cross-sectional view through a second embodiment of a valve stem pallet according to the invention. 
           [0017]      FIG. 8  is a perspective view of the valve stem pallet shown in  FIG. 7 . 
           [0018]      FIG. 9  is a flat pattern for a valve stem pallet in accordance with a third embodiment of the invention. 
           [0019]      FIG. 10  is a valve stem pallet made from the flat pattern shown in  FIG. 9 . 
           [0020]      FIG. 11  is a view of a valve stem pallet located in a finger follower having rotation limit stops for limiting a pivoting movement of the valve stem pallet. 
           [0021]      FIG. 12  is a cross-sectional view taken along lines  12 - 12  in  FIG. 11 . 
           [0022]      FIG. 13  is another embodiment of a finger follower having an arrangement for limiting rotation of the valve stem pallet. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0023]    Certain terminology is used in the following description for convenience only and is not limiting. The words “front,” “rear,” “upper” and “lower” designate directions in the drawings to which reference is made. The words “inwardly” and “outwardly” refer to directions toward and away from the parts referenced in the drawings. A reference to a list of items that are cited as “at least one of a, b, or c” (where a, b, and c represent the items being listed) means any single one of the items a, b, or c, or combinations thereof. The terminology includes the words specifically noted above, derivatives thereof and words of similar import. 
         [0024]      FIG. 1  shows a prior art finger follower  10  being acted on by cam  12 . The finger follower  10  pivots on and is in contact with a lash adjuster  14 , and through its pivot action operates on a valve stem  16  to open and close a valve in a cylinder of an internal combustion engine (not shown). The finger follower  10  pivots about a pivot point  18  formed on top of the lash adjuster  14 . The finger follower  10  has an outer elongated body  20  having a valve stem end  22 , a lash adjuster end  24 , and two elongated body side walls  26  and  28 . A first inner cavity  30  in the outer elongated body  20  is defined between the valve stem end  22 , the lash adjuster end  24  and the side walls  26  and  28 . Affixed to the outer elongated body  20 , at its lash adjuster end  24 , are lost motion spring pins  32  and  34 . Each of the side walls  26  and  28  provide lost motion spring stops  36  and  38 . 
         [0025]    An inner elongated body  40  is positioned in the first inner cavity  30 . The inner elongated body  40  has a first end which is pivotally attached to the valve stem end  22  of the outer elongated body  20 , by a pin  41 , a second end which is adjacent to the lash adjuster end  24 , and two inner elongated side walls. A center cam follower in the form of a roller  56  is mounted in the inner elongated body  40 . A latch assembly  58  forms part of the outer elongated body  20 . The latch assembly  58  is a conventional latch assembly which is operated in a conventional manner in order to lock the inner elongated body  40  to the outer elongated body  20  for transferring movement from the cam to the valve stem  16 . When the latch assembly  58  is unlocked, the cam movement simply results in the inner elongated body  40  pivoting up and down inside the outer elongated body. 
         [0026]    A lost motion torsional spring  60  is located between the inner and outer elongated bodies, and includes helical spring parts  62  and  63  positioned on pins  32  and  34  respectively. The action of the spring  60  is described in detail in U.S. Pat. No. 7.909,007, which is incorporated herein by reference as if fully set forth. 
         [0027]    Referring now to  FIGS. 2 and 3 , a finger follower  110  in accordance with the present invention is shown. The finger follower  110  according to the invention is similar to the prior art finger follower  10  in that it includes an outer elongated body  120  as well as an inner elongated body  140  which are connected together in a pivotable manner at the valve stem end  122  via a pin  141 . A lost motion spring  160  is provided connected to the spring holding pins  132  and  134  and has spring parts  162  and  163  as shown which act on spring pallets  152  and  154  on the inner elongated body  140  in order to maintain contact of the cam follower roller  156  with the cam (not shown). A latch assembly  158  is provided which, in a latched position, fixes the inner elongated body  140  in position relative to the outer elongated body  120 , and which can be released in order to allow movement between the inner and outer elongated bodies  140 ,  120 . 
         [0028]    As shown in detail in  FIGS. 2 and 3 , a valve stem pallet  170  is located between the two outer elongated body sidewalls  126 ,  128  and is connected in a rotational fixed manner to the pivot pin  141 . This connection can be via a press fit, splined fit, welding or any other suitable manner. The pivot pin  141  is slidably and rotatably located in the holes defined through the sidewalls  126 ,  128  of the outer elongated body  120  as well as the sidewalls  146 ,  148  of the inner elongated body  140 . The construction of the valve stem pallet  170  can be varied. In the embodiment shown in  FIGS. 2 and 3 , which is shown in detail in  FIG. 4 , the valve stem pallet  170  is a cold forged or machined part having a center lug  171  with downwardly extending sidewalls  172 ,  174  at each end in order to provide guides for capturing the end of the valve stem ( 16  in  FIG. 1 ). An opening  176  is defined through the lug  171  which is adapted for a press fit with the pin  141 . The bottom surface  182  of the lug  171  is a convex surface, preferably having a three dimensional curvature. The convex surface  182  can be formed as a partial spherical surface or any other suitable convex surface form. As shown in  FIG. 4 , rotation limiters in the form of projections  174 ,  175  extend from the sidewalls that are received in corresponding grooves  147 ,  149  defined on the inner surfaces of the sidewalls  146 ,  148  of the inner elongated body  140 . These rotation limiters prevent over-rotation of the valve stem pallet  170  while in use. By separately manufacturing the valve stem pallet  170 , this eliminates the need for forming a valve stem pallet as part of the outer elongated body as previously known in the art which involve higher manufacturing costs as well as more complex packaging. A preferred material for the pallet  170  is steel which is preferably surface hardened or heat treated at least in the area of the convex surface  182 . 
         [0029]    Referring to  FIGS. 5 and 6 , an alternate embodiment of a forged or machined valve stem pallet  170 ′ is shown. This embodiment is similar to the valve stem pallet  170 ; however, instead of the lug  171  with a single opening  176 , the sidewalls  172 ′,  174 ′ extend upwardly past a cross member  180 ′ on which the convex surface  182 ′ is defined. The sidewalls  172 ′,  174 ′ include aligned openings  176 ′,  178 ′ for receiving the pin  141 . This embodiment can offer reduced weight in comparison to the valve stem pallet  170 . Rotation limiters could also optionally be provided. 
         [0030]    Referring to  FIGS. 7 and 8 , a second embodiment of the valve stem pallet  190  is shown. The second embodiment of the valve pallet  190  is similar to the first embodiment except that it is formed as a turned part and includes a circular casing  192  with a cross member  196  extending across the medial portion. The upper end of the circular casing is deformed inwardly to form a top section  194  that engages with a connecter portion  198  that is affixed to the pin  141  via a press fit through an opening defined through the connecter portion  198 . The valve stem pallet  190  is preferably formed of steel and is hardened at least in the area of the cross member  196 . The cross member  196  can also have a convex form in the contact area for the valve stem  16 , in a similar manner as described in connection with the first embodiment of the valve stem pallet  170 . A further alternative is to locate the cross member  196  at the bottom of the circular casing  192 , eliminating any extension of the casing  192  past the convex contact area with the valve stem. 
         [0031]    Referring to  FIGS. 9 and 10 , the third embodiment of a valve stem pallet  200  is shown. The third embodiment of the valve stem pallet  200  is formed from sheet metal and can be made via a punched blank  202  shown in  FIG. 9 . The blank  202  is bent-up in order to form the flanges  204 ,  206  having holes  208 ,  210 , respectively defined therethrough for receiving the pin  141 . The base  212  extends between the flanges  204 ,  206 , and side members  214 ,  216  are bent around along the underside of the base in an area beneath the flanges  204 ,  206  in order to provide guides for maintaining the valve stem in position on the base  212  in use. The side members  214 ,  216  can be welded in place. The base  212  can be formed convexly in the area of contact with the valve stem by a stamping operation, and is preferably formed of steel and hardened, at least in the area of the base  212 . 
         [0032]    Referring now to  FIGS. 11 and 12 , an alternate embodiment of the finger follower  110  is shown in which the side walls  126 ,  128  of the outer elongated body  120  at the valve stem end  122  include rotation limiters  123  formed thereon. The rotation limiters  123  are preferably in the form of inwardly directed curved flanges having a curve or other shape adapted to limit a pivoting movement of the valve stem pallet  170 ′ via contact with adjacent edges of the sidewalls  172 ′,  174 ′ in a maximum pivoted position. In this embodiment, the inner elongated body  140  is formed with a single flange that extends between the side walls  172 ′,  174 ′ of the valve stem pallet  170 ′. The pin  141  has a press fit with the openings  176 ′,  178 ′ in the side walls  172 ′,  174 ′ of the valve stem pallet  170 ′ and a slip fit in the holes defined in both the outer elongated body  120  and the inner elongated body  140 . 
         [0033]    Referring now to  FIG. 13 , an alternate embodiment of the rotation limiter for the valve stem pallet  170 ′ is shown. In this embodiment, the pin  141 ′ includes a head  143 ′. The pin  141 ′ is press fit through the openings  176 ′,  178 ′ in the valve stem pallet  170 ′ and includes a slip fit with the corresponding holes in the outer elongated body  120  and the inner elongated body  140 . An anchor pin  145 ′ is connected through the head  143 ′ and into the side wall  128  of the outer elongated body  120  so that the valve stem pallet  170  is locked in rotation via the pin  141 ′ to the outer elongated body  120 . Alternatively, the anchor pin  145 ′ extends into a slot in the sidewall  128  so that a limited pivoting movement for the pin  141 ′ and the valve stem pallet  170 ′ is possible. This prevents excess or unwanted pivoting movement of the valve stem pallet  170 ′. Alternatively, instead of the pin  141 ′ with a head  143 ′, other means for fixation to the outer elongated body  120 , such as a keyed opening, welding, or any other suitable connection means. 
         [0034]    As a further alternative, the guides provided on the valve stem pallets discussed above that are adapted to capture the ends of the valve stem  16  can be eliminated from the valve stem pallets according to the invention, and instead be provided as downwardly directed extensions of the sidewalls  126 ,  128  or  146 ,  148  of the outer or inner elongated bodies  120 ,  140  on either side of the valve stem pallet that are adapted to capture an end of the valve stem. 
         [0035]    Having thus described the present invention in detail, it will be appreciated and apparent to those skilled in the art that many physical changes, only a few of which are exemplified in the detailed description of the invention, could be made without altering the inventive concepts and principles embodied therein. It is also to be appreciated that numerous embodiments incorporating only part of the preferred embodiment are possible which do not alter, with respect to those parts, the inventive concepts and principles embodied therein. The preferred embodiments and optional configurations are therefore to be considered in all respects as exemplary and/or illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all alternate embodiments and changes to this embodiment which come within the meaning and range of equivalency of said claims are therefore to be embraced therein.