Abstract:
An anti-rotation guide for a lifter in an overhead valve valvetrain. The anti-rotation guide includes a plug having two lobes connected through a neck region. A first lobe of the plug is held within a bore in the lifter. The bore forms an opening at the edge of the lifter through which the neck of the plug emerges. The bore in the lifter accommodates a first lobe of the plug that is wider than the opening in the edge of the lifter, whereby the plug is shaped to prevent its slipping from the lifter through the opening. The lifter reciprocates in a first bore in the cylinder head. The second lobe of the plug extends outward from the lifter into a second bore formed in the cylinder head and adjoining the first bore. The second lobe reciprocates in the second bore and limits rotation of the lifter.

Description:
PRIORITY 
       [0001]    The present application claim priority from US Provisional Application No. 62/219,268 filed Sep. 16, 2015. 
     
    
     FIELD 
       [0002]    The present teachings relate to valvetrains, particularly anti-rotation guides for lifters used in overhead valve (OHV) valvetrains. 
       BACKGROUND 
       [0003]    Some valvetrains include lifters that pass through a cylinder head to transmit force from a cam positioned under the cylinder head to a rocker arm position above the cylinder head. The lifter may include a roller follower that abuts and follows the cam and a cylindrical portion that reciprocates within a bore in the cylinder head. 
         [0004]    An anti-rotation guide may be used to maintain proper orientation of the roller-follower with respect to the cam. Examples of anti-rotation guides include a framing member positioned above the cylinder head and a pin and groove arrangement within the cylinder head. These designs may not always be reliable over the life of an engine. There continues to be a long felt need for anti-rotation guides that are compact, easy to manufacture, and highly reliable. 
       SUMMARY 
       [0005]    According to some aspects of the present teachings, an anti-rotation guide may be mounted to a lifter that is part of a valvetrain for an overhead valve (OHV) engine. The guide may have a profile that remains uniform over a portion of its length in a direction parallel to the lifter&#39;s axis. The profile may include a first region and a second region joined by a neck region. The first region may facilitate mounting the anti-rotation guide to the lifter. The second region extends via the neck region outward from the lifter. The first region may hold the anti-rotation guide to the lifter. The second region may fit within a guide channel formed in a cylinder head and maintain the orientation of the lifter as it reciprocates within the cylinder head. An anti-rotation guide according to these teachings may be securely held to the lifter, may reliably maintain orientation of the lifter, and have a low probability of interfering with reciprocation of the lifter. 
         [0006]    In some of these teachings, the cylinder head includes first and second bores. The first and second bores may be parallel to the lifter axis and overlap to form an opening between them. The lifter may be mounted to reciprocate within the first bore while the second region of the anti-rotation guide reciprocates within the second bore, including a portion of the second bore that is outside of the first bore. The cylinder head with the aforementioned bores provide a simple solution to manufacturing an engine that uses a lifter with an anti-rotation guide according to the present teachings. 
         [0007]    In some of these teachings, the first region of the anti-rotation guide may be mounted within a bore that is formed in the lifter itself. The bore in the lifter may be parallel to the lifter axis, extend partway through the length of the lifter, and intersect the edge of the lifter to form an opening in the edge of the lifter out of which the anti-rotation guide extends. The opening in the edge of the lifter may have a width less than the diameter of the bore in the lifter. This structure facilitates retention of the anti-rotation guide by the lifter. 
         [0008]    According to some aspects of the present teachings, an engine includes a cylinder head in which first and second bores are formed. The first and second bores are parallel and overlap to form an opening between them. A cylindrical portion of a lifter of a valvetrain is threaded through the first bore. A bore is formed in the lifter. The bore in the lifter has an axis parallel to that of the cylindrical portion and intersects an edge of the cylindrical portion to form an opening in an edge of the lifter. A plug in the bore in the lifter has a protrusion extending through the opening in the edge of the lifter. The protrusion is positioned to reciprocate within the second bore in the cylinder head and limit rotation of the lifter. 
         [0009]    In some of these teachings, the portion of the plug that is in the lifter has a greater width that the opening in the edge of the lifter. This may facilitate retention of the plug. In some of these teachings, the lifter has a greater width than the opening between the bores in the cylinder head. This may enhance functioning of the anti-rotation guide. 
         [0010]    In some of these teachings, the plug is retained in the bore in the lifter by a C-clip. In some of these teachings, the C-clip is held within a groove in the lifter that is formed about the perimeter of the bore in the lifter. The bore in the lifter may have an end that terminates within the cylindrical portion of the lifter to form a relatively flat end surface. The flat end surface may create a more consistent length within which the anti-rotation guide may be held the C-clip. The plug may be securely held between the C-clip and the relatively flat end surface. The plug may have a bulge that extends outward between two ends of the C-clip. The bulge may limit rotation of the C-clip, further securing the mounting of the plug to the lifter and minimizing the chance of interference between the cylinder block and parts mounted to the lifter. A plug with the desired bulge may be readily manufactured by cold-forming. In some alternative teachings, the plug is held to the lifter by a set screw. 
         [0011]    In some of these teachings, a groove is formed about the perimeter of the cylindrical portion of the lifter. The groove may provide an oil reservoir for maintaining lubrication of the lifter and the anti-rotation guide. In some of these teaching, the groove is at the height of the anti-rotation guide. An oil rifle may be formed in the cylinder block and let out on the first bore. In some of these teachings, the positioning of the oil rifle place it above the groove throughout the lifter&#39;s range of motion. This structure has been found to provide sufficient lubrication for the lifter and the anti-rotation guide while avoiding excessive oil consumption. 
         [0012]    The primary purpose of this summary has been to present broad aspects of the present teachings in a simplified form to facilitate understanding of the present disclosure. This summary is not a comprehensive description of every aspect of the present teachings. Other aspects of the present teachings will be conveyed to one of ordinary skill in the art by the following detailed description together with the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    Spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein to describe spatial relationships as illustrated in the figures. These relationships are independent from the orientation of any illustrated device in actual use. 
           [0014]      FIG. 1  illustrates part of an engine including a valvetrain having an anti-rotation guide according to some aspects of the present teachings. 
           [0015]      FIG. 2  illustrates the engine of  FIG. 1  with the cam off base circle. 
           [0016]      FIG. 3  illustrates a front view of the lower portion of a lifter according to some aspects of the present teachings. 
           [0017]      FIG. 4  illustrates a side view of the lifter of  FIG. 2 . 
           [0018]      FIG. 5  illustrates a partial cross-section of the engine of  FIG. 1  taken along the line  2 - 2 . 
           [0019]      FIG. 6  illustrates a partial cross-section of the engine of  FIG. 1  taken along the line  1 - 1 . 
           [0020]      FIG. 7  illustrates a partial cross-section of the engine of  FIG. 1  taken along the line  3 - 3 . 
           [0021]      FIG. 8  illustrates the partial cross-section of  FIG. 5  with the lifter removed. 
           [0022]      FIG. 9  illustrates the partial cross-section of  FIG. 5  with the anti-rotation guide removed. 
           [0023]      FIG. 10  illustrates a front view of the lower portion of a lifter according to some other aspects of the present teachings. 
           [0024]      FIG. 11  is a flow chart of a method according to some aspects of the present teachings. 
       
    
    
     DETAILED DESCRIPTION 
       [0025]      FIG. 1  illustrates a portion of an engine  110  that has an OHC valvetrain  112  according to some aspects of the present teachings. Engine  110  includes a cylinder head  117  having an upper surface  115  and a lower surface  133  (only parts of these structures are illustrated. The valvetrain  112  may include cam shaft  129 , cam  131 , lifter  113 , rocker arm  109 , rocker shaft  111 , and valve  103 . Valve  103  may control a port formed in cylinder head  117 . Lifter  113  is threaded through cylinder head  117  and may include a cam follower  127 . A cam follower  127  on lifter  113  may be biased against cam  131  by, for example, valve spring  107 . As shown by  FIG. 2 , rotation of cam shaft  129  may result in cam  131  driving lifer  113  upward. Lifter  113  may then cause rocker arm  109  to pivot on rocker shaft  111  and descend onto valve  103 , compressing valve spring  117  against upper surface  115  and lifting valve  109  off its seat  101  within cylinder head  117 . The present teachings may be applicable to any engine type having a lifter  113  that reciprocates within a cylinder head  117  or the like. But in some of these teachings, lifter  113  is part of an overhead valve (OHV) valvetrain  112 . In some of these teaching, lifter  113  includes a hydraulic lash adjuster (not shown). 
         [0026]      FIGS. 3 and 4  show a lower portion of lifter  113  in greater detail. Lifter  113  includes a cylindrical portion  143 . As shown in these figures, in some of the present teachings cam follower  127  is mounted proximate a lower end of cylindrical portion  143 . In some aspect of the present teachings, cam follower  127  is a roller follower. Cylindrical portion  143  may be positioned to reciprocate within a bore  119  formed in cylinder head  117 . According to some aspects of the present teachings, an anti-rotation guide  125  is mounted to lifter  113 . 
         [0027]      FIGS. 5-7  illustrate partial cross-sections of engine  110  along lines  2 - 2 ,  1 - 1 , and  3 - 3  of  FIG. 2  respectively. These lines and their positioning with respect to lifter  113  are also shown in  FIG. 4 .  FIG. 8  shows the partial cross-section of engine  110  along the line  2 - 2  with lifter  113  removed.  FIG. 9  shows the partial cross-section of engine  110  along the line  2 - 2  with just anti-rotation guide  125  removed. 
         [0028]    According to some aspects of the present teachings, a channel  123  is formed in cylinder head  117  and adjoining bore  119 , whereby there is an opening  160  of width  161  between channel  123  and bore  119  (see  FIG. 8 ). Channel  123  may be a cylindrical bore having a diameter  159  and an axis  5 . Bore  119  may be a cylindrical bore having a diameter  157  and an axis  4 . The axes  4  and  5  may be parallel and separated by a distance  167 . Distance  167  may be less than half the sum of diameter  157  and diameter  159 , whereby the two bores overlap. In some of these teachings, channel  123  is the smaller bore and is formed first. In some of these teachings, channel  123  extends only part way through cylinder head  117 . Channel  123  extends sufficiently through cylinder head  117  to allow free movement of anti-rotation guide  125  throughout the range of motion induced by rotation of cam  131 . In some of these teaching, channel  123  is further extended to allow lifter  113  to be raised beyond the lift of cam  131  to facilitate assembly of engine  110 . In some of these teachings, channel  123  is sufficiently long to allow lifter  113 , apart from cam follower  127 , to be raised to the height of surface  133  at its intersection with bore  119 . 
         [0029]    Cylindrical portion  143  of lifter  113  may have a diameter  122  nearly equal to but slightly less than the diameter  157  of bore  119  (see  FIGS. 3 and 8 ). In some of these teachings, the width  161  of the opening  160  between channel  123  and bore  119  is less than the diameter  122  of lifter  113 . In some of these teachings, width  161  is half or less diameter  122 . These dimensions may enhance the performance of anti-rotation guide  125 . 
         [0030]    According to some aspects of the present teachings, a channel  135  having a width  171  is formed in cylindrical portion  143  of lifter  113  (see  FIG. 9 ). Channel  135  may be a cylindrical bore having diameter  171 . Channel  135  may have an axis  175  that is parallel to axis  4  of bore  119 . Channel  135  overlaps an edge  177  of cylindrical portion  143  of lifter  113  to form an opening  172  of width  173 . 
         [0031]    According to some aspects of the present teachings, anti-rotation guide  125  has a substantially constant profile through a significant portion of its length when viewed along axis  4 . A significant portion is, for example, one fourth or more and could be the majority of the length. In some of these teachings, the profile includes a first region  150  having width  145  and a second region  148  of width  146  (see  FIG. 5 ). Regions  148  and  150  may be lobes and may be joined through a neck region  149  of width  147 . In some of these teachings, the width  147  of neck region  149  is less than the width  145  of first region  150 . The width  147  of neck region  149  may also be less than the width  146  of second regions  148 . 
         [0032]    According to some aspects of the present teachings, first region  150  of anti-rotation guide  125  is mounted within channel  135 . First region  150  of anti-rotation guide  125  may fit within and substantially plug a portion of the length of channel  135 . Because anti-rotation guide  125  may largely fill a length of channel  135  and, to a lesser extent, a length of channel  123 , anti-rotation guide  125  may be described as a plug. According to some aspects of the present teachings, width  145  of first region  150  is greater than the width  173  of opening  172  (see  FIGS. 5 and 9 ), whereby first region  150  cannot slip out of channel  135  through opening  172 . The width  145  of first region  150  may be nearly equal the diameter  171  of channel  135 . According to these teachings, the diameter  171  of channel  135  is also greater than the width  173  of opening  172 . 
         [0033]    According to some aspects of the present teachings, second region  148  of anti-rotation guide  125  is mounted to reciprocate within channel  123 . Neck region  149  of anti-rotation guide  125  may pass through opening  160  between bores  119  and  123  to join first region  150  and second region  148  of anti-rotation guide  125  (see  FIGS. 5 and 8 ). Accordingly, the width  147  of neck region  149  may be less than the width  161  of opening  160 . 
         [0034]    In some of these teachings, the width  161  of opening  160  is less than the width  171  of channel  135  in lifter  113 . In some of these teachings, first region  150  of anti-rotation guide  125  has a width  145  that is greater than the width  161  of opening  160 . In some of these teachings, first region  150  is sufficiently wide to form an interference fit with channel  135 . These characteristic may relate to enhanced functioning of anti-rotation guide  125 . 
         [0035]    According to some aspects of the present teachings, with first region  150  of anti-rotation guide  125  mounted within channel  135  of lifter  113 , second region  148  of anti-rotation guide can extend out of bore  119  and into channel  123  formed in cylinder head  117 , provided that lifter  113  has a suitable orientation with respect to cylinder head  117 . The relative shapes of second region  148  and channel  123  limit rotation of lifter  113 . In some of these teachings, second region  148  is shaped to permit lifter  113  to rotate several degrees while remaining within the confines of channel  123 . It has been determined that a degree of freedom to rotate does not interfere with the performance of a roller follower  127 . Allowing this degree of freedom increases manufacturing tolerances for the engine  110 . 
         [0036]    According to some aspects of the present teachings, channel  135  in cylindrical portion  143  of lifter  113  is formed only partway through cylindrical portion  143 , whereby channel  135  terminates within cylindrical portion  143  to form an end surface  124  (see  FIG. 3 ). In some of these teachings, channel  135  is formed in cylindrical portion  143  from end  140  and surface  124  is the distal end of channel  135 . Channel  135  may be formed in any suitable manner, such as drilling or milling. In some of these teaching, channel  135  is formed by milling, which allow surface  124  to be relatively flat. Relatively flat may be understood as being flatter than a typical surface formed by drilling, which would be no flatter than a  135  degree cone. Making surface  124  relatively flat facilitates fixedly mounting anti-rotation guide  125  in channel  135 . 
         [0037]    In some aspects of the present teachings, first region  150  of anti-rotation guide  125  is retained within channel  135  in lifter  113 . First region  150  of anti-rotation guide  125  may be retained within channel  135  in any suitable manner. In some of these teachings, of which lifter  113 A of  FIG. 10  provides an example, first region  150  is retained within channel  135  by a set screw  165  threaded through anti-rotation guide  125 . In some of these teachings, for which lifter  113  provides an example, first region  150  is retained within channel  135  by a C-clip  137 . In some of these teachings, C-clip  137  is positioned to press against end  126  of anti-rotation guide  125 , whereby anti-rotation guide  125  may be clamped between C-clip  137  and bore end surface  124  (see  FIG. 3 ). In some of these teachings, a groove  151  is provided about the periphery of channel  135  to receive and retain C-clip  137 . In some of these teachings, anti-rotation guide  125  has a bulge  139  (see  FIGS. 3 and 6 ). Bulge  139  may protrude between open ends  153  of C-clip  137  and limit rotation of C-clip  137 . 
         [0038]    Anti-rotation guide  125  may be formed in any suitable fashion. In some aspects of the present teachings, anti-rotation guide  125  is cold-formed. Anti-rotation guide  125  may be cold-formed from a cylindrical slug of metal. Cold-forming may include a series of stamping operations. A mold for one or more of these operations may include an opening through which a bulge  139  forms. 
         [0039]    In some of these teachings, a groove  141  is formed in the periphery of cylindrical portion  143  of lifter  113  (see  FIG. 3 ). Lifter  113  may have a range of motion within bore  119 . The range may be determined by the shape of cam  127 . In some of these teachings, an oil rifle  121  letting out onto bore  119  is formed in cylinder head  117  (see  FIGS. 1 and 2 ). In some of these teachings, groove  141  remains separated from oil rifle  121  throughout the range of motion of lifter  113 . For example, oil rifle  121  may remain above groove  141  through lifter  113 &#39;s range of motion. This configuration may facilitate maintaining good lubrication while avoiding excessive oil consumption. 
         [0040]      FIG. 11  provides a flow chart of a method  200  according to some aspects of the present teachings. Method  200  includes act  201 , forming channel  123  in cylinder block  117  and act  203 , forming bore  119  in cylinder block  117 . In some of these teachings, channel  123  is formed before bore  119 . In some of these teaching, channel  123  is formed only part way through cylinder block  117 . In some of these teachings, formation of channel  123  and bore  119  is initiated from lower surface  133  of cylinder block  117 . 
         [0041]    Method  200  further includes act  205 , boring channel  135  in lifter  113 . In some of these teachings, channel  135  is formed by milling. Act  207  is inserting anti-rotation guide  125  into channel  135 . Act  209  is retaining anti-rotation guide  125  within channel  135 . In some of these teachings, act  209  is installing C-clip  137 . In some of these teaching, act  209  is tightening set screw  165 . 
         [0042]    Method  200  continues with act  211 , aligning lifter  113  with bore  119  while aligning second region  148  of anti-rotation guide  125  with channel  123 . Act  211  enables subsequent act  213 , threading lifter  113  through cylinder block  117 , which is part of the process of installing rocker arm assembly  112  in engine  110 . Anti-rotation guide  125  may then maintain proper orientation of cam follower  127  with respect to cam  131 . 
         [0043]    The components and features of the present disclosure have been shown and/or described in terms of certain teachings and examples. While a particular component or feature, or a broad or narrow formulation of that component or feature, may have been described in relation to only some aspects of the present teachings or examples, all components and features in either their broad or narrow formulations may be combined with other components or features to the extent such combinations would be recognized as logical by one of ordinary skill in the art.