Abstract:
A switching roller finger follower, including: first and second rotatable outer arms; and a locking mechanism including a locking pin with a first outside diameter and first and second ends. The locking mechanism includes first and second locking sleeves: separate from the locking pin; fixedly secured to the first and second ends, respectively; and having second and third outside diameters, respectively, larger than the first outside diameter. The locking pin is displaceable such that: in a locked mode, the first and second locking sleeves contact the first and second outer arms, respectively, to block rotation of the first and second outer arms in a first rotational direction; and in an unlocked mode, the first and second locking sleeves are free of contact with the first and second outer arms, respectively.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent Application No. 61/757,489, filed Jan. 28, 2013, which application is incorporated herein by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a switching roller finger follower with a locking mechanism for use with a valve train of an internal combustion engine. In particular the locking mechanism includes locking sleeves with diameters selectable to control lash between a locking pin and outer arms contacting cam lobes. 
     BACKGROUND 
     A switching roller finger follower is used to control a valve in a valve train for an internal combustion engine. Arms for the follower are pivotably connected to a housing for the follower and positioned to enable contact with various lobes on a cam shaft. An element, such as a pin, in the follower is displaceable such that the element is either in a locked or an unlocked position with respect to the arms. In the locked position, respective ends of the element are aligned with respective arms such that when respective cam lobes contact the arms to pivot the arms, the arms engage the respective ends of the element. Since the engagement of the arms with the respective ends of the element locks the housing to the arms, the motion of the cam lobes is transferred to the housing to pivot the housing to operate (open and close) the valve. At the onset of the locked mode, when the respective ends of the element are aligned with the arms, but before the cam lobes begin to pivot the arms toward the elements, there is a gap, or lash, between the respective ends of the element and the arms. However, the dimensions of the respective ends of the element, such as the diameter, are subject to manufacturing and tolerance variations. Therefore, there is typically an unpredictable variation in the lash between the respective ends of the element and the outer arms for a single finger follower. 
     The same manufacturing and tolerance variations can causing varying amounts of unpredictable lash among finger followers in a production run of finger followers. The design of components for a cam shaft interfacing with the finger follower is impacted by the lash in the follower, for example, the design can optimize dimensions or configurations of components according to an expected lash. However, due to the unavoidable manufacturing and tolerance variations noted above, respective lash for individual followers in the production run cannot be predicted. As a result, the design of the components noted above must accommodate a larger range of possible lash dimensions, preventing optimization of the design. 
     Ideally, the lash for a finger follower would be as small as possible and would be identical for both ends of the element. However, due to the manufacturing and tolerance variations noted above, it is not possible to control the lash more tightly or predictably than within the range of the manufacturing and tolerance variations. That is, once the elements are installed, the lash variation is fixed and cannot be altered. Increased lash slows operation of the finger follower by requiring more time for the cam lobes to pivot the housing (operate the valve), since the amount of pivoting of the arm by the cam lobes to contact the elements and begin pivoting of the housing is increased. When the lash between the respective elements and arms is different, one cam lobe causes one of the arms to more quickly engage a respective end of the element than another cam lobe causes the other arm to engage the other end of the element, which can adversely affect operation of the finger follower. 
     In an unlocked mode, the respective ends of the element are misaligned with the arms, and the arms are free to pivot without contacting the elements. Thus, when the respective cam lobes on the cam shaft contact the outer arms, the arms pivot to accommodate the contact with the cam lobes and a position of the housing is not modified due to the contact between the cam lobes and the arms. In general, another cam contacts a different point, for example, the bearing, on the follower to displace the follower to operate the valve when the arms are in the unlocked mode. 
     To secure the element to the follower, retaining devices are affixed to ends of the element. In general, additional fabricating steps must be performed to provide features or profiles on the element to accommodate the retaining devices. For example, machined grooves are added to the ends to receive retaining rings. The extra fabricating steps and components add to the cost and complexity of the follower. 
     SUMMARY 
     According to aspects illustrated herein, there is provided a switching roller finger follower, including: first and second rotatable outer arms; and a locking mechanism including a locking pin with a first outside diameter and first and second ends. The locking mechanism includes first and second locking sleeves: separate from the locking pin; fixedly secured to the first and second ends, respectively; and having second and third outside diameters, respectively, larger than the first outside diameter. The locking pin is displaceable such that: in a locked mode, the first and second locking sleeves contact the first and second outer arms, respectively, to block rotation of the first and second outer arms in a first rotational direction; and in an unlocked mode, the first and second locking sleeves are free of contact with the first and second outer arms, respectively. 
     According to aspects illustrated herein, there is provided a switching roller finger follower, including: an inner housing with a space at least partially formed by first and second side walls, a locking barrel with a passageway including a sealed first end and a second end opening into the space, and first and second slots passing through material forming the first and second side walls, respectively; and first and second outer arms pivotably connected to the first and second side walls, respectively. The follower includes a locking mechanism with: a shuttle pin at least partially disposed in the passageway, including a notch disposed in the space, and displaceable within the passageway in a direction parallel to a longitudinal axis for the passageway; a locking pin including a first outside diameter, passing through the first and second slots and at least partly disposed in the notch, displaceable within the first and second slots, and including first and second ends extending past the first and second side walls, respectively; and first and second locking sleeves separately formed from the locking pin, fixedly secured to the first and second ends, respectively, having second and third outside diameters, respectively, and aligned with the first and second outer arms, respectively, in a direction orthogonal to a longitudinal axis for the locking pin. 
     According to aspects illustrated herein, there is provided a method of fabricating a switching roller finger follower, including: pivotably connecting first and second outer arms to an inner housing; disposing a shuttle pin, including a portion with a notch, within a passageway formed by the inner housing; disposing the notch within a space at least partly formed by the inner housing; disposing a locking pin, with a first outside diameter, in first and second slots in the inner housing; passing a portion of the locking pin through the notch; extending first and second ends of the locking pin past the inner housing; selecting second and third outside diameters for first and second locking sleeves, respectively, the second and third outside diameters greater than the first outside diameter; fixedly securing the first and second locking sleeves to the first and second ends of the locking pin, respectively; and aligning the first and second locking sleeves with the first and second outer arms, respectively, in a first direction orthogonal to a longitudinal axis for the locking pin. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various embodiments are disclosed, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, in which: 
         FIG. 1  is a perspective front view of a switching roller finger follower with a locking mechanism in a locked mode; 
         FIG. 2  is a perspective exploded view of an inner housing and locking mechanism for the switching roller finger follower of  FIG. 1 ; 
         FIG. 3  is a cross-sectional view of the switching roller finger follower with locking mechanism of  FIG. 1  in a locked mode; 
         FIG. 4  is a detail showing a locking pin and shuttle pin for the locking mechanism of  FIG. 1 ; 
         FIG. 5  is a cross-sectional view of the switching roller finger follower with locking mechanism of  FIG. 1  in an unlocked mode; and, 
         FIG. 6  is a perspective view of the switching roller finger follower with locking mechanism of  FIG. 1  in an unlocked mode and connected to a valve train. 
     
    
    
     DETAILED DESCRIPTION 
     At the outset, it should be appreciated that like drawing numbers on different drawing views identify identical, or functionally similar, structural elements of the disclosure. It is to be understood that the disclosure as claimed is not limited to the disclosed aspects. 
     Furthermore, it is understood that this disclosure is not limited to the particular methodology, materials and modifications described and as such may, of course, vary. It is also understood that the terminology used herein is for the purpose of describing particular aspects only, and is not intended to limit the scope of the present disclosure. 
     Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this disclosure belongs. It should be understood that any methods, devices or materials similar or equivalent to those described herein can be used in the practice or testing of the disclosure. 
       FIG. 1  is a perspective front view of a switching roller finger follower with locking mechanism  100  in a locked mode. 
       FIG. 2  is a perspective exploded view of an inner housing and locking mechanism  100  for the switching roller finger follower of  FIG. 1 . 
       FIG. 3  is a cross-sectional view of the switching roller finger follower with locking mechanism  100  of  FIG. 1  in a locked mode. 
       FIG. 4  is a detail showing a locking pin and shuttle pin for locking mechanism  100  of  FIG. 1 . The following should be viewed in light of  FIGS. 1 through 4 . Switching roller finger follower  102  includes locking mechanism  100  and inner housing  104  with space  106  at least partially formed by the inner housing, for example, by side walls  108  and  110  of the housing. The inner housing includes locking barrel  112  with passageway  114 . End E 1  of the passageway opens into the space and end E 2  is sealed, for example, by seal  115 . The inner housing includes slots  116  and  118  passing through material forming the inner housing, for example, material forming side walls  108  and  110 , respectively. The follower includes outer arms  120  and  122  pivotably connected to the inner housing, for example, at side walls  108  and  110 , respectively. In an example embodiment, pin  124  is used to connect the arms to the inner housing. 
     The locking mechanism includes shuttle pin  126 , locking pin  128 , and locking sleeves  130  and  132 . The shuttle pin is at least partially disposed in the passageway and includes notch  134  disposed in the space. The locking pin is disposed in, that is, passes through, slots  116  and  118  and is at least partly disposed in the notch. The locking pin includes ends  136  and  138  extending past side walls  108  and  110 , respectively, and has an outside diameter  140 . The locking sleeves are separate respective elements from the locking pin. Sleeve  130  is fixedly secured to end  136  and sleeve  132  is fixedly secured to end  138 . Sleeves  130  and  132  have respective outside diameters  142  and  144 . 
     The shuttle pin is displaceable along longitudinal axis  146  for the passageway to displace the locking pin as further described below. The locking pin includes longitudinal axis  148 . To enable contact of the locking sleeves with outer arms  120  and  122 , for example, as shown in  FIG. 1 , locking sleeves  130  and  132  are aligned with outer arms  120  and  122 , respectively, in direction D 1  orthogonal to axis  148 . Slots  116  and  118  are sized to enable movement of the locking pin in directions D 2  and D 3 , substantially parallel to axis  146 . 
     In a locked mode, as shown in  FIGS. 1 and 2 , locking sleeves  130  and  132  are in contact with arms  120  and  122 , respectively. As further described below, the contact of the sleeves and the arms fixes the arms with respect to the inner housing. 
       FIG. 5  is a cross-sectional view of switching roller finger follower  102  with locking mechanism  100  of  FIG. 1  in an unlocked mode. In the unlocked mode, the displacement of the locking pin causes locking sleeves  130  and  132  to move out of alignment with outer arms  120  and  122 , respectively. As further described below, the misalignment of the sleeves and subsequent lack of contact of the sleeves and the arms enables the arms to pivot with respect to the inner housing. 
     As noted above, lash is the amount of gap between, for example, sleeves  130  and  132  and outer arms  120  and  122  at the onset of the locked mode, caused by manufacturing and assembly variations. Also as noted above, the amount of lash helps determine the speed of operation of the follower, specifically; reducing the lash enables faster operation of the follower as further described below. As noted above, unequal lash for the two sides of a finger follower can adversely affect operation of the finger follower. Advantageously, diameters  142  and  144  are selectable to provide a predetermined amount of lash, to reduce or eliminate an undesirable amount of lash, and/or to equalize lash in response to tolerance variations associated with manufacture or assembly of the locking pin, the inner housing, or the outer arms. 
     For example, a determination is made as to the actual distance between the locking pin and the outer arms when the locking pin is installed in the locked mode. Diameters  142  and  144  are sized such that sleeves  130  and  132  take up as much of the actual distance as possible, such that a predetermined amount of distance is left between the sleeves and the outer arms in the locked mode, and/or lash for sleeves  130  and  132  is equal. Thus, lash is reduced or equalized to the greatest extent possible and/or to a predetermined amount. As a result, the speed of operation of follower  102  or the predictability and repeatability of the operation of follower  102  is increased to the greatest extent possible, while minimizing possible adverse affects due to unequal lash. Also, since diameters  142  and  144  are selectable to such that lash is known and predictable, the design of components for a camshaft interfacing with follower  102  can be optimized according to the known and predictable lash. 
     In an example embodiment, outside diameters  142  and  144  are the same. In an example embodiment, outside diameter  142  is different from outside diameter  144 . Thus, lash can be individually adjusted for each sleeve/outer arm pair. 
       FIG. 6  is a perspective view of switching roller finger follower  102  with locking mechanism  100  of  FIG. 1  in an unlocked mode and connected to a valve train. The following should be viewed in light of  FIGS. 1 through 6 . Follower  102  includes contact surface  150  and attachment portion  152  arranged to pivotably connect the inner housing to a support element. In an example embodiment, the follower includes bearing  154 . The contact surface is arranged to contact valve stem  156 . In the locked mode, cam lobes  158  and  160  of a cam shaft (not shown) for a valve train, including valve stem  156 , are arranged to contact outer arms  120  and  122 , in particular contact surfaces  162  and  164 , respectively. Since the outer arms are locked in place by the sleeves, the pressure applied by the cam lobes causes the follower to pivot in direction RD 1  with respect to portion  152 . Via contact surface  150 , the follower pushes the stem in direction D 4 , for example, to open a valve including the valve stem. A greatest amount of pivoting of follower  102  occurs when portions  158 A and  160 A are in contact with surfaces  162  and  164 , respectively. 
     When the cam lobes rotate further, for example from portion  158 A to portion  158 B contacting surface  162 , spring  172  is able to pivot follower  102  in direction RD 2 . Springs  166  and  168  urge arms  120  and  122  in rotational direction RD 3  to maintain contact between outer arms  120  and  122  and cams  158  and  160 , respectively 
     In the unlocked mode, when the cam lobes contact the outer arms, the arms are free to pivot about pin  124 , for example, in direction RD 4 . Thus, the contact between the cam lobes and the outer arms is accommodated by the pivoting such that contact between the cam lobes and the outer arms does not cause the housing to displace with respect to the support element. Therefore, the cam lobes do not cause the follower to operate the valve. Springs  166  and  168  urge arms  120  and  122 , respectively, in direction RD 3  to ensure that arms  120  and  122  are in position to receive sleeves  130  and  132 , respectively, for the locking mode. 
     In an example embodiment, a different cam lobe, for example cam lobe  170 , is arranged to contact the bearing (which is rotational with respect to the inner housing, but otherwise fixed to the housing, for example by pin  169 ) such that the contact of cam lobe  170  with the bearing causes the follower to pivot in direction RD 1  with respect to the support element to push the valve stem in direction D 4 . In an example embodiment, in the absence of force applied by the follower to the valve stem in direction D 4 , spring  172  urges the valve stem in direction D 5 . The operation of cam lobes  158 ,  160 , and  170  vary the height to which valve  156  is opened during operation. 
     Returning to  FIGS. 3 and 5 , the shuttle pin is operated as is known in the art. For example, spring  174  is located in space  106  and in contact with the shuttle pin. The spring urges the shuttle pin in direction D 3 . Port  176  is used to supply and remove pressurized fluid in portion  114 A of the space. When pressurized fluid is present in portion  114 A, the fluid forces the shuttle pin in direction D 2  such that the locking pin is shifted to the locked mode. When pressurized fluid is absent from portion  114 A, the spring forces the shuttle pin in direction D 3  such that the locking pin is shifted to the unlocked mode. 
     It will be appreciated that various of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.