Patent Publication Number: US-10323549-B2

Title: Self-aligning rocker arm and pushrod design

Description:
TECHNICAL FIELD 
     The present disclosure relates generally to rocker arms that are used in engines that mate with other components such as pushrods in order to move other components of the engine. More specifically, the present disclosure relates to a self-aligning rocker arm and pushrod design wherein the rocker arm has features that guide the pushrod or other component that mates with the rocker arm to stay functionally engaged with the rocker arm. 
     BACKGROUND 
     Many engines, including diesel engines used by locomotives and the like, using valve trains to control the timing of the opening and closing of intake and/or exhaust valves. As can be imagined, the timing of opening or closing these valves is important to make the engine run properly. These valve trains may use a cam shaft that actuates a cam follower rocker arm that moves a pushrod up and down, which in turn, causes one end of an overhead rocker arm to move up and down. This creates a rocking motion of the overhead rocker arm so that the other end opposite the end engaged by the pushrod, also moves up and down. This end of the overhead rocker arm may move a valve member so that the valve member opens and closes at the appropriate time. 
     As can be imagined, such valve trains are assembled to create the engine or after maintenance has been performed on the engine and/or valve train. During the assembly process, the pushrod is typically seated or otherwise mated to a surface of a depression of a rocker arm. Once properly aligned, bolts are torqued on a rocker bridge member that keeps the rocker arm, pushrod, and other components of the valve train in place. 
     However, in some instances, the pushrod is not always completely properly seated on the pad or button of the rocker arm when the bolts are torqued. As a result, the pushrod may slide off the rocker arm or may be bent as the bolts are torqued as an unintended compressive load is applied to the pushrod. In some cases, the portion of the rocker arm contacting the pushrod may also become damaged. This may cause the engine to malfunction or be damaged further once the engine is turned on, etc. 
     Accordingly, it is desirable to develop an apparatus and/or method to help prevent improper assembly of the valve train such that the pushrod is properly mated or aligned with a feature of a rocker arm. 
     SUMMARY OF THE DISCLOSURE 
     A rocker arm according to an embodiment of the present disclosure for use with train assembly of an engine is provided. The rocker arm may comprise a body defining a pivot aperture and including a pad spaced away from the pivot aperture a predetermined distance. The pad may include a peripheral surface and a top surface that defines a blind aperture, forming an intersection therewith, and the top surface may include a plurality of aligning features disposed around the blind aperture. 
     A valve train assembly according to an embodiment of the present disclosure is provided. The valve train assembly may comprise a cam follower rocker arm including a body that comprises a large eye portion defining a pivot aperture and a pad spaced away from the pivot aperture a predetermined distance, a small eye portion disposed underneath the pad, and the small eye portion defines a roller aperture. The pad may include a peripheral surface and a top surface that defines a blind aperture forming an intersection therewith, and the top surface includes at least one aligning feature disposed around the blind aperture. The pad includes an oblong shape with a major axis and a minor axis, the pivot aperture defines a pivot axis that is parallel with the minor axis and the major axis is perpendicular to the pivot axis, and the pad defines a maximum width measured along the major axis. The blind aperture defines a diameter measured along the major axis and the body defines a ratio of the maximum width to the diameter ranging from 2.3 to 2.9. The valve train further comprises a first shaft disposed in the pivot aperture, a roller disposed in the roller aperture, an overhead follower rocker arm including a first end, a second end, and a pivot feature located between the first end and the second end, a second shaft engaging the pivot feature of the overhead follower rocker arm, a pushrod including a bottom end engaging the pad and a top end engaging the first end of the overhead follower rocker arm, and a valve bridge assembly engaging the second end of the overhead follower rocker arm. 
     A method of assembly for a train assembly using a rocker arm according to an embodiment of the present disclosure is provided. The method may comprise engaging a pushrod with an aligning feature of a rocker arm or an aperture of the rocker arm, and limiting the movement of the pushrod relative to the rocker arm so that the pushrod is always in contact with an aligning feature of the rocker arm or an aperture of the rocker arm. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a rocker arm with self-aligning features according to an embodiment of the present disclosure after being finished by machining. 
         FIG. 2  is a rear view of a forging of a rocker arm used to create the rocker arm of  FIG. 1  before being machined. 
         FIG. 3  is a rear oriented perspective view of the rocker arm of  FIG. 1 . 
         FIG. 4  is a sectional view of the rocker arm of  FIG. 3  taken along a midplane of the rocker arm, revealing the lubrication bores and self-aligning features of the rocker arm more clearly. 
         FIG. 5  is a perspective view of a valve train assembly used in an engine employing the rocker arm of  FIG. 1 . 
         FIG. 6  is an alternate perspective view of the valve train assembly of  FIG. 5 . 
         FIG. 7  is a sectional view of the valve train assembly of  FIGS. 5 and 6  showing the extreme positions of the pushrod as the pushrod contacts the self-aligning features of the rocker arm when the roller attached to the rocker arm contacts with the base circle portion of the cam shaft of the valve train assembly. 
         FIG. 8  is a sectional view of the valve train assembly of  FIGS. 5 and 6  showing the extreme positions of the pushrod as the pushrod contacts the self-aligning features of the rocker arm when the roller attached to the rocker arm contacts a lobe over the cam shaft of the valve train assembly. 
       It should be noted that in  FIGS. 5  thru  8 , two positions of the same pushrod are illustrated engaging the pad of the cam follower rocker arm. The purpose of showing these two positions of the pushrod is to illustrate the principles of how proper alignment of the pushrod with respect to a rocker arm is maintained during assembly and operation of the valve train assembly. However, the reader should understand that only one pushrod per rocker arm is actually utilized. 
         FIG. 9  contains a flowchart depicting a method of assembly for a valve train using a rocker arm according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to embodiments of the disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. In some cases, a reference number will be indicated in this specification and the drawings will show the reference number followed by a letter for example,  100   a ,  100   b  or a prime indicator such as  100 ′,  100 ″ etc. It is to be understood that the use of letters or primes immediately after a reference number indicates that these features are similarly shaped and have similar function as is often the case when geometry is mirrored about a plane of symmetry. For ease of explanation in this specification, letters or primes will often not be included herein but may be shown in the drawings to indicate duplications of features discussed within this written specification. 
     A method for assembling a valve train assembly, the resulting valve train assembly, and rocker arm having aligning features that may be used with such valve train assemblies or other train assemblies of an engine will now be described. While the application discussed herein is primarily for the valve train assembly of a diesel engine used by locomotives, it is to be understood that in other embodiments the engine may be any type of internal combustion engine and the train assembly may be used to control the movement of other engine components such as fuel injectors, etc. Also, the rocker arm herein may be used in any situation where a rocker arm is employed regardless of whether it is moved by a cam shaft directly or indirectly, etc. 
     Referring now to  FIGS. 1, 3 and 4 , a rocker arm  200  having aligning features according to an embodiment of the present disclosure will now be described. The aligning features are so called as these features bias a pushrod or other similar component toward a seating feature such as an aperture of the rocker arm and usually form an oblique angle with the sidewall or axis of an aperture of the rocker arm as will be described momentarily. The rocker arm  200  may comprise a body  202  that defines a pivot aperture  204  and includes a pad  206  (may also be referred to as a button, cup or seat portion) spaced away from the pivot aperture  204  a predetermined distance  208 . The pad  206  may include a peripheral surface  210  and a top surface  212  that defines a blind aperture  214 , forming an intersection therewith, and the top surface  212  may include at least one aligning feature  216 . 
     For many embodiments, a plurality of aligning features  216  are provided that are disposed near and around the blind aperture  214 . The pad  206  further may further include a bottom flat surface  218  disposed at the bottom of the blind aperture  214  and a cylindrical sidewall  220  extending from the bottom flat surface  218  to the top surface  212  of the pad  206 . A groove  222  may be provided at the intersection of the bottom flat surface  218  and the cylindrical sidewall  220  for various reasons such as to avoid corner interference with the end of a pushrod or other similar component or the distribution of lubrication at the joint formed between the pushrod or other similar component and the rocker arm. 
     In other embodiments such as those shown in  FIGS. 7 and 8 , the pad  206  may include a concave surface  224  defining the blind aperture  214  such that a distinct sidewall or bottom surface does not exist. Such a concave surface  224  may be a radial surface that is configured to match complimentarily a convex surface at the end of a pushrod or other similar component. Other than this difference, the pad  206  of the rocker arm  200 ′ of  FIGS. 7 and 8 , and the rocker arm  200 ′ in general, may be similarly or identically configured to the rocker arm  200  of  FIGS. 1, 3 and 4 . 
     As best seen in  FIGS. 1 and 4 , the blind aperture  214  defines a perimeter  226  at the intersection of the blind aperture  214  with the top surface  212  of the pad  206  and the plurality of aligning features  216  includes a first chamfered surface  228  extending from the perimeter  226  of the blind aperture  214  towards the peripheral surface  210  of the pad  206 . The plurality of aligning features  216  may further include a second chamfered surface  230  extending substantially from the peripheral surface  210  of the pad  206  (a small radius  234  may be provided to transition from the peripheral surface to the second chamfered surface) toward the first chamfered surface  228 , forming an oblique angle α with the first chamfered surface  228  (see  FIG. 4 ). Focusing on  FIG. 4 , this oblique angle α may range from 160 to 180 degrees and may be approximately 170 degrees in certain embodiments. Also, the first chamfered surface  228  may form an obtuse angle β with the sidewall  220 . This angle β may range from 110 to 120 degrees and may be approximately 115 degrees in certain embodiments. The plurality of aligning features  216  may further include a radial surface  232  transitioning from the first chamfered surface  228  to the second chamfered surface  230 . 
     With continued reference to  FIGS. 1, 3 and 4 , the rocker arm  200  may include a plurality of lubrication bores  236  for distributing lubrication to areas where joints are formed with other components such as shafts and pushrods, etc. The pad  206  may include a generally elliptical or oblong shape with a major axis  238  and a minor axis  240  (see  FIG. 1 ). The pivot aperture  204  may define a pivot axis  242  that is parallel with the minor axis  240  and the major axis  238  is perpendicular to the pivot axis  242  and the minor axis  240 . The pad  206  defines a maximum width  244  measured along the major axis  238  and the blind aperture  214  defines a diameter D 214  measured along the major axis  238  and the ratio of the maximum width  244  to the diameter D 214  may range from 2.3 to 2.9 and may be approximately 2.6 in some embodiments. 
     As best seen in  FIG. 1 , the rocker arm  200  may further comprise a large eye portion  246  defining the pivot aperture  204  and a small eye portion  248  disposed underneath the pad  206 . That is to say, the small eye portion  248  may define a roller aperture  250  with an axis of rotation A 250  and the cylindrical axis A 214  of the blind aperture  214  of the pad  206  intersects axis A 250 , being perpendicular thereto. The small eye portion  248  may be split forming a first ring portion  252  and a second ring portion  254  on opposite sides of the rocker arm  200  separated by a cavity  256  (see  FIG. 4 ), both of which may define a roller aperture  250  that extends through both the first ring and the second ring portions  252 ,  254 . 
     Referring now to  FIG. 2 , a forged blank  300  used to create the rocker arm  200  of  FIG. 1  can be seen. As shown, the forged blank  300  lacks some finished dimensions and features created by machining the forged blank  300 . The machined features  302  are shown in  FIGS. 1, 3 and 4  and include the pad  206  and its peripheral surface  210 , top surface  212 , blind aperture  214 , aligning features  216 , various blending radii, the roller aperture  250 , cavity  256 , etc. Also, a step  258  may be machined to form the width of the large eye portion, measured along the pivot axis  242  so that when one rocker arm is contacting another adjacent rocker arm as they are inserted onto a shaft, these machined surfaces touch, accurately controlling the stack up dimensions of the plurality of adjacent rocker arms. The material used to make the forged blank  300  may be any suitable material such as steel, iron, grey cast iron, etc. 
     Referring now to  FIGS. 5 and 6 , a valve train assembly  400  that may use a rocker arm  200  such as that just described with reference to  FIGS. 1  thru  4  is shown. The valve train assembly  400  may comprise a cam follower rocker arm  402  similarly or identically configured to the rocker arm  200  just described. 
     Accordingly, as best seen in  FIGS. 1, 3 and 4 , the cam follower rocker arm  402  (may also be referred to as the lower rocker arm) may include a body  202  that comprises a large eye portion  246  defining a pivot aperture  204  and a pad  206  spaced away from the pivot aperture  204  a predetermined distance  208 , and a small eye portion  248  disposed underneath the pad  206 , defining a roller aperture  250  as previously described. The pad  206  may include a peripheral surface  210  and a top surface  212  that defines a blind aperture  214  and the top surface  212  includes one or more aligning features  216  disposed around or near the blind aperture  214 . The pad  206  includes an oblong or elliptical shape with a major axis  238  and a minor axis  240 , the pivot aperture  204  defines a pivot axis  242  that is parallel with the minor axis  240  and the major axis  238  is perpendicular to the pivot axis  242 , and the pad  206  defines a maximum width  244  measured along the major axis  238  and the blind aperture  214  defines a diameter D 214  measured along the major axis  238  and the ratio of the maximum width  244  to the diameter D 214  may range from 2.3 to 2.9. 
     Looking back at  FIGS. 5 and 6 , a first shaft  404  (may be referred to as a lower shaft) is disposed in the pivot aperture  204  of the rocker arm  200 . Similarly, the valve train assembly  400  may further comprise a roller  406  disposed in the roller aperture  250  of the rocker arm (see  FIGS. 7 and 8 ). Returning to  FIGS. 5 and 6 , an overhead follower rocker arm  408  (may be referred to as an upper rocker arm) may also be provided including a first end  410 , a second end  412 , and a pivot feature  414  located between the first end  410  and the second end  412 . A second shaft  416  (may also be referred to as an upper shaft) engages the pivot feature  414  of the overhead follower rocker arm  408 , and more particularly, may be inserted into the pivot feature  414  of the overhead follower rocker arm  408 . The overhead follower rocker arm  408  is differently configured as compared to the cam follower rocker arm  402  but it is contemplated that it could have a similar or identical configuration to the cam follower rocker arm  402  in other embodiments. More specifically, the overhead follower rocker arm could have a pad that is similarly or identically constructed with aligning features as has been already described with reference to the cam follower rocker arm. 
     The valve train assembly  400  may further include a pushrod  418  including a bottom end  420  engaging the pad  206  of the cam follower rocker arm  402  and a top end  422  engaging the first end of the overhead follower rocker arm. A valve bridge assembly  424  may also be provided engaging the second end  412  of the overhead follower rocker arm  408 . Though not clearly shown, the valve bridge assembly  424  is operatively connected to a valve member such that movement of the overhead follower rocker arm  408  will open and close the valve member at the appropriate time. As can be seen, there are two such valve bridge assemblies  424 ,  424 ′ adjacent each other that have adjacent overhead follower rocker arms  408 ,  408 ′ that rock back and forth at different times so as one valve bridge assembly is in an open configuration, that is to say, the valve member associated with that valve bridge assembly is an open configuration to allow the ingress or egress of gases, the other valve bridge assembly is in a closed configuration. 
     In order to cause the movement of the valve bridge assemblies  424 , the valve train assembly  400  further comprises a cam shaft  426  engaging the roller  406  disposed in the roller aperture of the cam follower rocker arm  402 . As the cam shaft  426  rotates, a lobe  428  of the cam shaft  426  will contact the cam follower rocker arm  402  of one valve train assembly  400 , causing that pushrod  418  to move upwards, creating the rocking motion of the associated overhead follower rocker arm  402 , opening the appropriate valve. As the cam shaft  426  continues to rotate, the lobe  428  passes the cam follower rocker arm  402  allowing the valve to close. Eventually, another lobe  428 ′ of the cam shaft  426  contacts the adjacent cam follower rocker arm  402 ′, causing the adjacent valve train assembly  400 ′ to move and open another valve at the appropriate time. 
     As also shown in  FIGS. 5 and 6 , the valve train assembly  400  further comprises a cylinder head  430  and a rocker bridge  432  that is operatively connected to the cylinder head  430  and engages the second shaft  416 , holding the second shaft  416  stationary. Though not shown completely, the cylinder head  430  may be attached such as by fastening to the engine block (not shown). More specifically, two bolts  434  are provided that attach the cylinder head  430  to the engine block, holding the cylinder head  430 , rocker bridge  432 , overhead follower rocker arm  408  and pushrods  418  in place. Furthermore, guide sleeves  436  (may also be referred to as pushrod covers) are provided and each guide sleeve  436  defines a guide bore (not shown) and the pushrod  418  is disposed in the guide bore of the guide sleeve  436 . There is clearance between the guide bore and the pushrod, so the guide sleeve only provides minimal alignment. 
     A sheet metal member  438  is provided, at least partially covering the lower components of the valve train assembly  400  including the cam follower rocker arms  402 , first shaft  404 , and the cam shaft  426 . The sheet metal member  438  defines a plurality of slots  440  strategically positioned over each set of cam follower rocker arms  402 . An access cover plate  442  is positioned over the slot  440  and the pushrod  418  extends through the access cover plate  442 , while at the same time, the guide sleeve  436  is positioned between the access cover plate  442  and the cylinder head  430 . 
     During assembly, the pushrod  418  is inserted into the guide sleeve  436  until it engages the aligning features of the pad of the cam follower rocker arm  402 . Then, the overhead follower rocker arm  408  and the second shaft  416  are positioned properly so that the pushrods  418  are properly engaging the overhead follower rocker arms  408  and the second shaft  416  is sitting on a bearing member  444  sandwiched between the cylinder head  430  and second shaft  416 . As the bolts  434  are torqued to the specified setting, the rocker bridge  432  presses on the flat portions  446  of the second shaft  416 , which in turn causes the second shaft  416  to press on the concave surface  448  of the bearing member  444 , which in turn presses down on the cylinder head  430  and engine block. 
     During the assembly process, if the aligning features are not present on the pad, the pushrod may fall off the pad or may not be seated properly in a retaining feature (such as a blind aperture of the pad). If the pushrod is stuck, the compressive load exerted on the pushrod when the bolts are torqued may bend the pushrod, making the valve train assembly unable to work properly, or may otherwise damage a portion of the rocker arm. By providing the aligning features, dimensions or ratios described herein, the pushrod may be unable to fall off the pad or may be biased into the proper seated position on the pad of the rocker arm as the bolts are torqued, helping to prevent the valve train assembly from malfunctioning. To that end, it may be helpful in certain embodiments if the maximum width  244  of the pad  206  ranges from 70 mm to 80 mm (see  FIG. 4 ) in some embodiments. 
     It should be noted that in  FIGS. 5  thru  8 , two positions of the same pushrod are illustrated engaging the pad of the cam follower rocker arm. The purpose of showing these two positions of the pushrod are to illustrate the principles of how proper alignment of the pushrod with respect to a rocker arm is maintained during assembly and operation of the valve train assembly. However, the reader should understand that only one pushrod per rocker arm is actually utilized. 
     Focusing now on  FIGS. 7 and 8 , the extreme positions of the pushrod as the cam shaft rotates are depicted. In  FIG. 7 , the possible extreme left position  450  of the pushrod  418  when the roller  406  is contacting the base circle portion  452  of the cam shaft  426  is limited by the internal bore of the guide sleeve  436  such that bottom end  420  of the pushrod  418  is in contact with the second chamfered surface  230 , biasing the pushrod  418  toward the blind aperture  214 . On the other hand, the possible extreme right position  454  of the pushrod  418  when the roller  406  is contacting the base circle portion  452  of the cam shaft  426  is limited by the internal bore of the guide sleeve  436  such that the bottom end  420  of the pushrod  418  contacts the first chamfered surface  228  or the radial surface  232 , biasing the pushrod  418  toward the blind aperture  214 . 
     Conversely,  FIG. 8  shows the possible extreme positions of the pushrod  418  when the lobe  428  of the cam shaft  426  contacts the roller  406 . The possible extreme left position  450 ′ of the pushrod  418  in this case is limited by the internal bore of the guide sleeve  436  such that the bottom end  420  of the pushrod  418  is in contact with the first chamfered surface  228  or the radial surface  232 , biasing the pushrod  418  toward the blind aperture  214  of the pad  206  of the rocker arm  200 ,  402 . On the other hand, the possible extreme right position  454 ′ is limited by the internal bore of the guide sleeve  436  such that the bottom end  420  of the pushrod  418  contacts the second chamfered surface  230  of the pad  206  of the rocker arm  200 ′,  402 , biasing the pushrod  418  toward the blind aperture  214 . 
     Any of the variables, dimensions, configurations of various components or features of those components, ratios etc. discussed herein may vary from what has been specifically mentioned as needed or desired. 
     INDUSTRIAL APPLICABILITY 
     In practice, a rocker arm according to any embodiment described herein may be provided, sold, manufactured, and bought etc. to refurbish, retrofit or remanufacture existing valve train assemblies and engines. Similarly, an engine, a valve train assembly or other type of train assembly may also be provided, sold, manufactured, bought, etc. to provide a new apparatus. 
       FIG. 9  is a flow chart delineating a method of assembly for a valve train assembly or other similar assembly using a rocker arm according to an embodiment of the present disclosure. The method  500  may comprise: engaging a pushrod with an aligning feature of a rocker arm or an aperture of the rocker arm (step  502 ), and limiting the movement of the pushrod relative to the rocker arm so that the pushrod is always in contact with an aligning feature (step  504 ). The method may further comprise torquing a fastener operatively associated with the pushrod and the rocker arm to a predetermined threshold without bending the pushrod or forcing the pushrod off the rocker arm (step  506 ). 
     In some embodiments, step  504  may include providing a guide sleeve with an internal bore, through which the pushrod passes, limiting the lateral movement of the pushrod (step  508 ). 
     In other embodiments, step  504  may include providing a stop feature on the rocker arm around an alignment feature or an aperture of the rocker arm (step  510 ). The stop feature may be a ridge or the like. 
     In yet further embodiments, step  504  may be omitted altogether. 
     It will be appreciated that the foregoing description provides examples of the disclosed assembly and technique. However, it is contemplated that other implementations of the disclosure may differ in detail from the foregoing examples. All references to the disclosure or examples thereof are intended to reference the particular example being discussed at that point and are not intended to imply any limitation as to the scope of the disclosure more generally. All language of distinction and disparagement with respect to certain features is intended to indicate a lack of preference for those features, but not to exclude such from the scope of the disclosure entirely unless otherwise indicated. 
     Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments of the apparatus and methods of assembly as discussed herein without departing from the scope or spirit of the invention(s). Other embodiments of this disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the various embodiments disclosed herein. For example, some of the equipment may be constructed and function differently than what has been described herein and certain steps of any method may be omitted, performed in an order that is different than what has been specifically mentioned or in some cases performed simultaneously or in sub-steps. Furthermore, variations or modifications to certain aspects or features of various embodiments may be made to create further embodiments and features and aspects of various embodiments may be added to or substituted for other features or aspects of other embodiments in order to provide still further embodiments. 
     Accordingly, this disclosure includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the disclosure unless otherwise indicated herein or otherwise clearly contradicted by context.