Abstract:
A hybrid valve lifter guide formed of metal and nonmetallic material for maintaining the angular position of a reciprocable valve lifter having a circumferential surface with at least one alignment flat. The guide includes a metal guide body having a longitudinal guide wall with at least one guide opening through the wall. The guide opening is adapted to receive a valve lifter. A nonmetallic insert is retained by the body adjacent the guide opening to engage at least one alignment flat of the valve lifter received in the guide opening to substantially maintain the angular position of the valve lifter and dampen angular oscillation of the lifter during engine operation.

Description:
TECHNICAL FIELD 
     This invention relates to valve lifter guides for an internal combustion engine and, more particularly, to a guide assembly having a metal lifter guide with plastic inserts for dampening valve lifter oscillation and maintaining the angular position of roller hydraulic valve lifters within the engine. 
     BACKGROUND OF THE INVENTION 
     Engines with roller valve lifters require a valve lifter guide to maintain alignment between the roller of the valve lifter and an associated camshaft. For cost and assembly considerations, lifter guides are typically designed to accommodate multiple valve lifters on a common bank of cylinders. These guides are manufactured having straight-edged guide openings that engage flats on opposite sides of the lifters. With metal guides, the spacing of the opening edges is slightly larger than the valve lifter flats to avoid binding. However, tolerance variations can result in excessive clearance between the valve lifter and the metal guide, allowing a higher degree of valve lifter oscillation than desired. 
     One solution is to use valve lifter guides made of fully composite material to have a tight initial fit on the valve lifter flats. The composite guides take a “set” during engine break in which then results in good alignment without excessive friction load. This compliance and “set” in the composite lifter guide is predetermined and calibrated by the selection of constituents used to make up and process the composite material. 
     In some engines that use cylinder-deactivation with switching valve lifters, fully composite valve lifter guides are impractical due, for example, to space limitations in the engines and high initial drag. In this case, metal construction valve lifter guides are the only practical choice. 
     SUMMARY OF THE INVENTION 
     The present invention provides a hybrid valve lifter guide formed of metal and nonmetallic material for dampening valve lifter oscillation and maintaining the angular position of a roller valve lifter while overcoming the limitations of the prior art. Specifically, the valve lifter guide may be used with any type of internal combustion engine, including engines with space limitations and switching lifters for cylinder deactivation. 
     In an exemplary embodiment, the hybrid valve lifter guide is designed to accommodate multiple hydraulic switching valve lifters in a push rod type internal combustion engine with cylinder deactivation. Each valve lifter has a generally cylindrical body having upper and lower ends. A lost motion spring extends from the upper end and a roller cam follower bearing is attached to the lower end of the valve lifter. Four axially-extending flats are machined into the circumferential surface of each valve lifter at 90 degree intervals. The flats provide guiding surfaces adapted to engage the guide to prevent excessive angular rotation of the valve lifters during engine operation. 
     The valve lifter guide has a metal guide body having a longitudinal guide wall with multiple guide openings, extending through the wall, each adapted to receive a valve lifter as described above. The guide body may have upturned stiffening side rails extending from laterally opposite sides of the guide wall. A nonmetallic insert is retained by the guide body adjacent each guide opening to engage at least one alignment flat of a valve lifter received in each guide opening to dampen valve lifter oscillation and maintain the angular position of the valve lifter within the guide opening. 
     In an exemplary embodiment for an engine having two valves per cylinder, the guide openings are arranged in pairs having longitudinally adjacent ends separated by a laterally extending cross member. Each guide opening is further defined by a by a bulbous end portion spaced longitudinally from the cross member and a pair of laterally-spaced straight edges extending longitudinally between the cross member and the bulbous end portion. The edges of the guide openings are adapted to engage opposite flats of valve lifters received within the guide openings. 
     In one exemplary embodiment, the insert is formed of glass filled nylon and has first and second ends joined by opposite sidewalls adapted to engage flats of adjacent valve lifters. The insert has a generally C-shaped cross section internally defining a retaining channel adapted for attachment to the cross member. 
     In an alternative embodiment, protrusions extend from the first and second ends of the insert to snap into openings or recesses in the upturned side rails of the lifter guide. 
     When a pair of valve lifters are received within a pair of guide openings, one flat of each valve lifter engages an adjacent sidewall of the insert, retained at the adjacent ends of the guide openings. Also, a pair of oppositely facing flats of each valve lifter adjacent the insert are positioned to engage the straight edges of their respective guide openings. The engagement between the flats of the valve lifters and the edges of the guide openings and sidewalls of the insert dampen valve lifter oscillation and maintain the angular position of the valve lifters as they reciprocate within the guide openings. 
     If desired, additional inserts may be attached to the lifter guide oppositely spaced from the adjacent ends of the guide openings, so that a sidewall of each of the additional inserts engages a fourth flat of an associated valve lifter spaced away from the adjacent ends of each pair of guide openings. The additional inserts provide each valve lifter with a fourth guide, which further improves the lifter guides ability to dampen valve lifter oscillation and maintain the angular position of the valve lifters as they reciprocate within the guide openings. 
     These and other features and advantages of the invention will be more fully understood from the following description of certain specific embodiments of the invention taken together with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a pictorial view of a switching valve lifter shown adjacent an associated cam; 
         FIG. 2  is an exploded pictorial view of a valve lifter and guide assembly according to the present invention; 
         FIG. 3  is a view similar to  FIG. 2  showing an alternative embodiment of valve lifter guide assembly; 
         FIG. 4  is a view similar to  FIG. 3  showing a variation of the valve lifter guide assembly of  FIG. 3 ; and 
         FIG. 5  is a pictorial view of the valve lifter and guide assembly of  FIG. 4  together with an associated camshaft. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring first to  FIG. 1  of the drawings in detail, numeral  10  generally indicates a switching type valve actuating assembly including a camshaft  11  and a hydraulic switching valve lifter  12  as used in a push rod type internal combustion engine. The valve lifter  12  has a generally cylindrical body  13  having upper and lower spaced ends  14 ,  16 . A lost motion spring  18  extends from the upper end  14  of the valve lifter to urge the valve lifter against a cam  19  during cylinder deactivation. A cam follower roller  20  is mounted in the lower end  16  of the valve lifter  12  to minimize friction between the valve lifter and an associated cam  19 . Four axially extending flats  22  are machined into the circumferential surface of the cylindrical body  13  at 90 degree intervals. The flats  22  form guiding surfaces to maintain the angular relation of the valve lifter  12  to the cam  19  during engine operation. 
       FIG. 2  shows a valve lifter and guide assembly  26  including a plurality of switching valve lifters  12  retained in a valve lifter guide  30 . The lifter guide  30  includes a metal guide body  32  having a longitudinal guide wall  34  with guide openings  36  arranged in spaced pairs. The openings  36  of each pair have longitudinally adjacent ends  38  separated by a laterally extending cross member  40 . The guide openings  36  are further defined by bulbous end portions  42  spaced longitudinally from the cross members  40  and pairs laterally spaced straight edges  44 ,  46  extending longitudinally between the cross members and the bulbous end portions. The edges  44 ,  46  act as guides, which engage opposite flats  22  of the valve lifters  12 . The metal guide body also has a pair of upturned side rails  48 ,  50  extending from laterally opposite sides of the guide wall  34 . If desired, the metal guide body  32  may be hardened to improve resistance to scuffing and wear. 
     The valve lifter guide  30  also includes a plurality of elongated inserts  54 , only one being shown. Inserts  54  are formed of nonmetallic material such as plastic or glass filled nylon. The inserts have spaced ends  56 ,  58  connected by sidewalls  60 ,  62 , which engage one of the flats  22  of the valve lifters. Each insert  54 , has a generally C-shaped cross section internally defining a retaining channel  64  adapted for receiving one of the cross members  40 . 
     The lifter guide  30  is assembled by first snapping the inserts  54  over the cross members  52 , which are received in the retaining channels  64 , to form the valve lifter guide assembly  26 . Valve lifters  12  are then inserted into the bulbous end portions  42  of guide openings  36 . The valve lifters  12  are then slid toward their adjacent cross member  40  so that one of the flats  22  of the valve lifters  12  engages a sidewall  60  or  62  of each insert  54  and adjacent oppositely positioned flats  22  of the valve lifters  12  engage with clearance the edges  44 ,  46  of the guide openings  36 . 
     After the valve lifters  12  and guide assembly  26  are completed, the assembly may be installed within an engine block, not shown. When the assembly  26  is installed in the engine block, the lower ends  16  of the valve lifters  12  fit into bores beneath the valve lifter guide assembly and the rollers  20  engage cams of an associated camshaft, not shown. 
     During engine operation, rotation of a camshaft  11  causes the cams  19  to reciprocate the valve lifters  12  within the guide openings  36  for valve train actuation. Depending on the speed of valve lifter reciprocation, the lost motion spring  18  may cause the valve lifters  12  to oscillate angularly, thereby placing angular loads on the inserts  54  and the edges  44 ,  46  of the guide openings  36 . 
     As the valve lifters  12  oscillate within the guide openings  36 , the inserts  54  initially absorb the oscillations and the angular loads of the valve lifters  12  to minimize the loads exerted on the edges  44 ,  46 . When the load exerted by the valve lifters  12  increases sufficiently, as at high engine speeds, the inserts will yield and allow oscillations of the valve lifters  10  to exert increased force against the edges  44 ,  46  of the guide openings  36 . However, the inserts still act to dampen the oscillations and angular loads exerted by the lifters  12  and reduce the load exerted on the edges  44 ,  46  of the guide openings  36 . 
     Since the lifter guide  30  and the edges  44 ,  46  are formed of metal, the edges are able to resist greater rotational loads than the inserts  54 . Thus, the edges  44 ,  46  resist the increased rotational loads exerted by the valve lifters  12  and maintain the angular positions of the valve lifters  12  relative to their respective cams  19 . 
     It is preferred, that the inserts  54  should have a tight initial fit around the valve lifters  12  and take a “set” during engine break in. The compliance and “set” of the inserts  54  is predetermined and calibrated by the selection of constituents used to make up and process the inserts. Preferably, the predetermined “set” should maintain a tight tolerance between the insert  54  and an associated valve flat  22  to maintain good alignment of the valve lifters  12  without exerting excessive resistance to restrict the movement of the valve lifters. 
       FIG. 3  illustrates a valve lifter and guide assembly  68  having a plurality of switching valve lifters  12  retained in an alternative valve lifter guide  70  similar to lifter guide  30 , wherein like numerals indicate like parts. Lifter guide  70  has a metal guide body  71  like that of lifter guide  30  in having a longitudinal guide wall  34  with guide openings  36  arranged in pairs having longitudinally adjacent ends  38  separated by a laterally extending cross member  40 . The guide openings  36  again include bulbous end portions  42  spaced longitudinally from cross members  40  and pairs of laterally spaced straight edges  44 ,  46  extending longitudinally between the cross members and the bulbous ends. The edges  44 ,  46  act as guides, which engage opposite flats  22  of the valve lifters  12 . The metal guide body also has a pair of upturned side rails  48 ,  50  extending from laterally opposite sides of the guide wall  34 . If desired, the metal guide body  32  may be hardened to improve resistance to scuffing and wear. 
     The valve lifter guide  70  also includes a plurality of elongated inserts  72 , only one being shown. Inserts  72  are formed of nonmetallic material such as plastic or glass filled nylon. The insert  72  have spaced ends  74 ,  76  connected by sidewalls  78 ,  80  engaging the flats of the valve lifters  12 . Protrusions  82  extend from the ends  74 ,  76  of the insert  72 . The protrusions  82  are adapted to be snapped into openings or recesses  84  provided in the side rails  40 ,  42 . 
     The guide  70  is assembled by first attaching inserts  72  to the lifter guide body  71  by snapping the protrusions  82  of the inserts  72  into the recesses  84  of the rails  40 ,  42 . After the inserts are attached to the lifter body  71 , valve lifters  12  are placed in the guide  70  to form the lifter and guide assembly  68 . The valve lifters  12  are inserted into the bulbous ends  42  of the guide openings  36 . The lifters  12  are then subsequently slid toward their adjacent cross members  40  so that one of the flats  22  of each valve lifter  12  engages one of the sidewalls  78 ,  80  of the associated insert  72  and adjacent oppositely positioned flats  22  of the valve lifter engage with clearance the edges  44 ,  46  of the guide openings  36 . 
     The lifter guide assembly  68  and the valve lifters  12  retained within the guide openings  36  are then installed within an engine block, not shown. When the assembly  68  is installed in the engine block, the lower ends  16  of the valve lifters  10  fit into bore beneath the valve lifter guide to engage cams of a camshaft, not shown. 
     The operation of guide assembly  68  is similar to the operation of guide assembly  26  as explained above. 
     Referring now to  FIGS. 4 and 5 , a fragmentary portion of an engine  90  is shown in exploded and assembled conditions, respectively. Engine  90  includes a camshaft  11  with cams  19  engaged by switching valve lifters  12  of a valve lifter and guide assembly  92 . Assembly  92  includes an alternative valve lifter guide  94  similar to lifter guide  70 , wherein like numerals indicate like parts. Guide  94  has a metal guide body  96  having a longitudinal guide wall  34  with guide openings  36  arranged in pairs having longitudinally adjacent ends  38  separated by a laterally extending cross member  40 . The guide openings  36  are further defined by bulbous end portions  42  spaced longitudinally from cross members  40  and a pair of laterally spaced straight edges  44 ,  46  extending longitudinally between the cross members and the bulbous ends. The edges  44 ,  46  act as guides, which engage opposite flats  22  of the valve lifters  12 . The metal guide body  96  also has a pair of upturned side rails  48 ,  50  extending from laterally opposite sides of the guide wall  34 . If desired, the metal guide body  96  may be hardened to improve resistance to scuffing and wear. 
     The valve lifter guide  94  also includes elongated inserts  72 , formed of nonmetallic material such as plastic or glass filled nylon. The inserts  72  have spaced ends  74 ,  76  connected by opposite sidewalls  78 ,  80  adapted to engage flats of the valve lifters  12 . Protrusions  82  extend from the ends  74 ,  76  of the inserts  72 . The protrusions  82  are adapted to be snapped into openings or recesses  84  provided in the side rails  40 ,  42 . 
     The guide  94  is assembled by first attaching inserts  72  to the guide body  96 , adjacent the cross members  40 , by snapping the protrusions  82  of the inserts  72  into the recesses  84  of the rails  40 ,  42 . After the inserts are attached to the lifter guide body  96 , valve lifters  12  are inserted into the bulbous ends  42  of the guide openings  44 . The valve lifters  12  are then slid toward the cross member  40  so that one of the flats  22  of each valve lifter  12  engages one of the sidewalls  78 ,  80  of the inserts  72  and adjacent oppositely positioned flats  22  of the valve lifters engage edges  44 ,  46  of the associated guide openings  36 . 
     Additional inserts  72  are then attached to the guide body  96  by snapping the protrusions  82  of the inserts  72  into additional recesses  84  spaced a distance from the cross members  40  so that the inserts are positioned adjacent the fourth flats  22  of the valve lifters retained within the guide openings  36  to enclose the valve lifters within the guide openings  36 , and complete the lifter and guide assembly  92 . 
     The guide assembly  92 , with the valve lifters  12  is then installed in an engine block, not shown. When the guide assembly  92  is installed in the engine, the lower ends  16  of the valve lifters  12  extend into bores beneath the valve lifter guide assembly and the rollers  20  engage their respective cams  19 . 
     Guide assembly  92  operates similarly to guide assembly  26 , except that the additional inserts  72  increase the ability of the guide to dampen oscillation of the valve lifters  12 . Further, the additional inserts  72  retain the valve lifters within the guide openings  36  before the guide assembly  92  and its valve lifters  12  are installed in an engine. If the rotational loads of the valve lifters  12  become excessive, the inserts  72  on opposite sides of the valve lifters may give, while still dampening the oscillating loads of the valve lifters, to allow the edges  44 ,  46  to limit the rotational movement of the valve lifters  12  and maintain the angular relationship between the roller bearings  20  and their respective cams  19 . 
     While the invention has been described by reference to certain preferred embodiments, it should be understood that numerous changes could be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the disclosed embodiments, but that it have the full scope permitted by the language of the following claims.