Patent Publication Number: US-2018045081-A1

Title: Switching rocker arm assembly having eccentric axle for lash adjustment

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of International Application No. PCT/US2016/029515 filed Apr. 27, 2016 which claims the benefit of U.S. patent application Ser. No. 62/153,004 filed on Apr. 27, 2015. The disclosure of the above application is incorporated herein by reference. 
    
    
     FIELD 
     The present disclosure relates generally to switching roller finger followers or rocker arms in internal combustion engines. 
     BACKGROUND 
     Variable valve actuation (WA) technologies have been introduced and documented. One WA device may be a variable valve lift (VVL) system, a cylinder deactivation (CDA) system such as that described in U.S. Pat. No. 8,215,275 entitled “Single Lobe Deactivating Rocker Arm” hereby incorporated by reference in its entirety, or other valve actuation systems. Such mechanisms are developed to improve performance, fuel economy, and/or reduce emissions of the engine. Several types of the WA rocker arm assemblies include an inner rocker arm within an outer rocker arm that are biased together with torsion springs. 
     Switching rocker arms allow for control of valve actuation by alternating between latched and unlatched states. A latch, when in a latched position causes both the inner and outer rocker arms to move as a single unit. When unlatched, the rocker arms are allowed to move independent of each other. In some circumstances, these arms can engage different cam lobes, such as low-lift lobes, high-lift lobes, and no-lift lobes. Mechanisms are required for switching rocker arm modes in a manner suited for operation of internal combustion engines. 
     The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure. 
     SUMMARY 
     A switching rocker arm assembly constructed in accordance to one example of the present teachings includes an outer arm, an inner arm, a bearing axle and a pivot axle. The outer arm can have a first outer side arm and a second outer side arm. The outer arm can define outer bores. The inner arm can have a first inner side arm and a second inner side arm. The inner arm can be disposed between the first and second outer side arms. The inner arm can define inner bores. The bearing axle can support a bearing. The pivot axle can cooperate with the outer and inner arms. One of the bearing axle and pivot axle comprises (i) a central axle body having a central centerline, (ii) a first axle end body having a first centerline and (iii) a second axle end body having a second centerline. The central centerline is offset from at least one of the first and second centerlines. 
     According to additional features, the central axle body locates between the first and second inner side arms. The central centerline can be offset relative to the first and second centerlines a distance equal to a desired mechanical lash adjustment desired in the switching rocker arm assembly. The first and second centerlines are coaxial. The pivot axle is eccentric. The switching rocker arm assembly can further comprise an elephant foot (e-foot). The e-foot is assembled between the central axle body of the pivot axle and the valve. Rotation of the pivot axle causes the e-foot to move relative to the valve. The pivot axle defines a tool engaging feature on one of the first and second axle end bodies. The pivot axle secures the inner arm to the outer arm while also allowing a rotational degree of freedom wherein one of the outer and inner arms rotates relative to the other of the outer and inner arms about the pivot axle when the switching rocker arm assembly is in a deactivated state. One of the inner and outer rocker arms defines a passage that extends to a corresponding bore that receives the pivot axle. 
     According to other features, the switching rocker arm can further comprise a securing member disposed through the passage that fixes the pivot axle relative to the one of the inner and outer rocker arms subsequent to setting lash. The securing member can comprise flowable plastic that is configured to solidify. The pivot axle can define an annular groove around one of the first and second axle end bodies. The securing member locates within the annular groove. 
     In one configuration the bearing axle is eccentric. The bearing is configured to engage a cam lobe. Rotation of the bearing axle causes the bearing to move relative to the cam lobe to adjust mechanical lash. The bearing axle is supported on opposite ends by torsion spring ends. One of the inner and outer rocker arms defines a passage. The switching rocker arm can further comprise a securing member disposed through the passage that fixes the bearing axle relative to the one of the inner and outer rocker arms subsequent to setting lash. The bearing axle defines an annular groove around one of the first and second axle end bodies. The securing member locates within the annular groove. 
     A rocker arm constructed in accordance to additional features includes an outer arm, a bearing axle and a pivot axle. The outer arm can have a first outer side arm and a second outer side arm, the outer arm defining outer bores. The bearing axle can extend through the first and second outer side arms and that supports a bearing. The pivot axle that pivotally supports the outer arm. One of the bearing axle and pivot axle comprises (i) a central axle body having a central centerline, (ii) a first axle end body having a first centerline and (iii) a second axle end body having a second centerline. The central centerline is offset from at least one of the first and second centerlines. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is a front perspective view of an exemplary switching rocker arm incorporating a pivot axle constructed in accordance to one example of the present disclosure, the switching rocker arm shown with an exemplary valve and lash adjuster; 
         FIG. 2  is a perspective view of the switching rocker arm of  FIG. 1  constructed in accordance to one example of prior art; 
         FIG. 3  is a first perspective view of the pivot axle of  FIG. 2 , the pivot axle having an eccentric profile; 
         FIG. 4  is a second perspective view of the pivot axle of  FIG. 2 ; 
         FIG. 5  is a sectional view of the pivot axle, inner rocker arm and outer rocker arm according to one configuration of the present disclosure; 
         FIG. 6  is a side view of the switching rocker arm of  FIG. 2 ; 
         FIG. 7  is a sectional view of the switching rocker arm of  FIG. 6 ; 
         FIG. 8  is am exploded perspective view of an inner rocker arm and an outer rocker arm of a switching rocker arm constructed in accordance to another example of the present disclosure; 
         FIG. 9  is a perspective view of a roller bearing axle having an eccentric profile and constructed in accordance to another example of the present disclosure; and 
         FIG. 10  is a sectional view of the bearing axle, inner rocker arm and outer rocker arm of  FIG. 8 . 
     
    
    
     DETAILED DESCRIPTION 
     With initial reference to  FIGS. 1-2 , an exemplary switching rocker arm constructed in accordance to one example of prior art is shown and generally identified at reference  10 . The switching rocker arm assembly  10  can be a compact cam-driven single-lobe cylinder deactivation (CDA-1L) switching rocker arm installed on a piston-driven internal combustion engine, and actuated with the combination of a duel-feed hydraulic lash adjusters (DFHLA)  12  that receive oil from oil control valves (“OCV”, not shown). The switching rocker arm assembly  10  can be engaged by a single lobe cam  20 . The switching rocker arm assembly  10  can include an inner arm  22  and an outer arm  24 . The default configuration is in the normal-lift (latched) position where the inner arm  22  and the outer arm  24  are locked together, causing an engine valve  26  to open and allowing the cylinder to operate as it would in a standard valvetrain. The DFHLA  12  has two oil ports. A lower oil port  28  provides lash compensation and is fed engine oil similar to a standard HLA. An upper oil port  30 , referred as the switching pressure port, provides the conduit between controlled oil pressure from the OCV and a latch  32 . When the latch  32  is engaged, the inner arm  22  and the outer arm  24  operate together like a standard rocker arm to open the engine valve  26 . In the no-lift (unlatched) position, the inner arm  22  and the outer arm  24  can move independently to enable cylinder deactivation. 
     A pair of lost motion torsion springs  40  are incorporated to bias the position of the inner arm  22  so that it always maintains continuous contact with the camshaft lobe  20 . The torsion springs  40  are secured to mounts located on the outer arm  24  by spring retainers  44 . The spring retainers  44  retain the torsion springs  40  laterally. The lost motion torsion springs  40  require a higher preload than designs that use multiple lobes to facilitate continuous contact between the camshaft lobe  20  and an inner arm bearing  50  having a roller follower  52 . 
     The outer arm  24  can have a first outer side arm  64  and a second outer side arm  66 . The inner arm  22  can be disposed between the first outer side arm  64  and the second outer side arm  66 . The inner arm  22  can have a first inner side arm  70  and a second inner side arm  72 . The inner arm  22  and the outer arm  24  are both mounted to a pivot axle  74 . The pivot axle  74  can be located adjacent to a first end of the rocker arm assembly  10 , which secures the inner arm  22  to the outer arm  24  while also allowing a rotational degree of freedom pivoting about the pivot axle  74  when the rocker arm assembly  10  is in a deactivated state. As will be described herein, the pivot axle  74  has an eccentric geometry that allows the pivot axle  74  to rotate about its central axis within the inner and outer arms  22 ,  24  adjusting lash of the rocker arm assembly  10  between the valve  26  and the roller follower  52 . 
     The bearing  50  and roller follower  52  are mounted between the first inner side arm  70  and the second inner side arm  72  on a bearing axle  80  that, during normal operation of the rocker arm assembly  10  serves to transfer energy from the rotating cam  20  to the rocker arm assembly  10 . The bearing axle  80  is biased upwardly by bearing axle springs  40 . 
     With further reference now to  FIGS. 3-7 , additional features of the present disclosure will be described. Mechanical lash can be set mechanically with a valve tip cap  100 . It will be appreciated that a plurality of valve tip caps  100  may be provided having different geometries. A suitable valve tip cap  100  can be assembled between an elephant foot (e-foot)  102  and the engine valve  26  ( FIG. 1 ) to take up the variance on the rocker arm assembly  10  between the engine valve  26 , the cam  20  and the DFHLA  12 . In one configuration, the use of such valve tip caps  100  may be eliminated with the use of the pivot axle  74 . Although, in some configurations the pivot axle  74  may be used in concert with a valve tip cap  100 . 
     The pivot axle  74  includes a central axle body  110 , a first axle end body  112  and a second axle end body  114 . The central axle body  110  can be undercut and have a central outer surface  116 . The first axle end body  112  and the second axle end body  114  have corresponding first and second centerlines  122  and  124 . The first and second centerlines  122  and  124  can be coaxial. The central axle body  110  has a central centerline  130 . The central centerline  130  is not coaxial with the first and second centerlines  122  and  124 . In this regard, as the pivot axle  74  is rotated around the first and second centerlines  122  and  124 , the central axle body  110  will also rotate but while altering the position of the central outer surface  116 . In other words, because the central centerline  130  is offset from the first and second centerlines  122  and  124 , the central outer surface  116  of the central axle body  110  will move positions relative to the first axle end body  112  and the second axle end body  114 . It will be appreciated that other shapes of the central axle body  110  are contemplated that allow the central outer surface  116  to move radially upon rotation of the pivot axle  74  around the centerlines  122  and  124 . 
     During rotation of the pivot axle  74 , as the central outer surface  116  moves locations, the e-foot  102  will also move. As the e-foot  102  moves toward and away from the valve  26 , lash can be set. It will be appreciated that during the rotation, the first and second axle end bodies  112  and  114  ride within inner arm bores  132  in the inner rocker arm  122  and outer arm bores  134  in the outer rocker arm  24 . During rotation of the pivot axle  74 , the locations of the first and second rocker arms  22  and  24  are unchanged. The first axle end body  112  includes a tool engaging groove  140 . A tool can engage the tool engaging groove  140  for imparting rotational motion on the pivot axle  74  during the lash adjustment. While not shown, a similar tool engaging groove may be incorporated on the second axle end body  114 . The second axle end body  114  can define an annular groove  142 . Once a desired lash has been set, the pivot axle  74  can be locked from further rotation. 
     With particular reference now to  FIGS. 2 and 5 , additional features of the present disclosure will be described. The outer rocker arm  24  can define a passage  160  that extends from an outer surface  162  of the outer rocker arm  24  to the outer arm bore  134 . Once the desired lash has been set, a securing member in the form of flowable plastic  170  can be injected through the passage  160 . The plastic  170  can solidify in the bore  134  and around the groove  142  to fix the pivot axle  74  relative to the outer rocker arm  24  and preclude axial movement of the pivot axle  74 . Explained further, the plastic  170  precludes translation of the pivot axle  74  along the axes  122 ,  124 . Moreover, the plastic  170  precludes rotational movement of the pivot axle  74  around the axes  122 ,  124  precluding radial movement of the pivot axle  74 . The desired lash therefore is now fixed. It will be appreciated that other configurations may be employed for fixing the pivot axle  74  relative to the outer rocker arm  24  once the desired lash is set. 
     With reference now to  FIGS. 8-10 , a switching rocker arm constructed in accordance to additional features is shown and generally identified at reference numeral  210 . The switching rocker arm  210  can be configured for use in a CDA- 1 L such as described above with respect to  FIG. 1 . The switching rocker arm assembly  210  can include an inner arm  222  and an outer arm  224 . The default configuration is in the normal-lift (latched) position where the inner arm  222  and the outer arm  224  are locked together, causing an engine valve (see  26 ,  FIG. 1 ) to open and allowing the cylinder to operate as it would in a standard valvetrain. When a latch  232  is engaged, the inner arm  222  and the outer arm  224  operate together like a standard rocker arm to open the engine valve. In the no-lift (unlatched) position, the inner arm  222  and the outer arm  224  can move independently to enable cylinder deactivation. A pair of lost motion torsion springs  240  are incorporated to bias the position of the inner arm  222  so that it always maintains continuous contact with a camshaft lobe (see  20 ,  FIG. 1 ). The torsion springs  240  are secured to mounts located on the outer arm  224  by spring retainers  244 . The spring retainers  244  retain the torsion springs  240  laterally. The lost motion torsion springs  240  require a higher preload than designs that use multiple lobes to facilitate continuous contact between the camshaft lobe  220  and an inner arm bearing  250  having a roller follower  252 . 
     The outer arm  224  can have a first outer side arm  264  and a second outer side arm  266 . The inner arm  222  can be disposed between the first outer side arm  264  and the second outer side arm  266 . The inner arm  222  can have a first inner side arm  270  and a second inner side arm  272 . The inner arm  222  and the outer arm  224  are both mounted to a pivot axle  274 . The pivot axle  274  can be located adjacent to a first end of the rocker arm assembly  210 , which secures the inner arm  222  to the outer arm  224  while also allowing a rotational degree of freedom pivoting about the pivot axle  274  when the rocker arm assembly  210  is in a deactivated state. 
     The bearing  250  and roller follower  252  are mounted between the first inner side arm  270  and the second inner side arm  272  on a bearing axle  280  that, during normal operation of the rocker arm assembly  210  serves to transfer energy from the rotating cam  220  to the rocker arm assembly  210 . The bearing axle  280  is biased upwardly by bearing axle springs  240 . The bearing axle  280  of the rocker arm assembly  210  has an eccentric geometry that allows the bearing axle  280  to rotate about its central axis within the inner and outer arms  222 ,  224  adjusting lash of the rocker arm assembly  210 . 
     The bearing axle  280  includes a central axle body  310 , a first axle end body  312  and a second axle end body  314 . The central axle body  310  can be undercut and have a central outer surface  316 . The first axle end body  312  and the second axle end body  314  have corresponding first and second centerlines  322  and  324 . The first and second centerlines  322  and  324  can be coaxial. The central axle body  310  has a central centerline  330 . The central centerline  330  is not coaxial with the first and second centerlines  322  and  324 . In this regard, as the bearing axle  280  is rotated around the first and second centerlines  322  and  324 , the central axle body  310  will also rotate but while altering the position of the central outer surface  316 , therefore altering the position of the bearing  250  and a resulting location of contact between the bearing  250  with the cam (see  20 ,  FIG. 1 ). This movement allows the system mechanical lash to be adjusted and set. In other words, because the central centerline  330  is offset from the first and second centerlines  322  and  324 , the central outer surface  316  of the central axle body  310  will move positions relative to the first axle end body  312  and the second axle end body  314 . It will be appreciated that other shapes of the central axle body  310  are contemplated that allow the central outer surface  316  to move radially upon rotation of the bearing axle  280  around the centerlines  322  and  324 . 
     During rotation of the bearing axle  280 , the first and second axle bodies  312  and  314  ride around a surface of the bearing axle springs  240 . During rotation of the bearing axle  280 , the locations of the first and second rocker arms  222  and  224  are unchanged, while the relative location of the bearing  250  changes. The second axle end body  314  includes a tool engaging groove  340 . A tool can engage the tool engaging groove  340  for imparting rotational motion on the bearing axle  280  during the lash adjustment. While not shown, a similar tool engaging groove may be incorporated on the second axle end body  314 . The second axle end body  314  can define an annular groove  342 . Once a desired lash has been set, the bearing axle  280  can be locked from further rotation. 
     The inner rocker arm  222  can define a passage  360  that extends from an outer surface  362  of the inner rocker arm  222  to a bearing axle bore  364 . Once the desired lash has been set, a securing member in the form of flowable plastic  370  can be injected through the passage  360 . The plastic  370  can solidify in the bore  364  and around the groove  342  to fix the bearing axle  280  relative to the inner rocker arm  222  and preclude axial movement of the bearing axle  280 . Explained further, the plastic  370  precludes translation of the bearing axle  280  along the axes  322 ,  324 . Moreover, the plastic  370  precludes rotational movement of the bearing axle  280  around the axes  322 ,  324  precluding radial movement of the bearing axle  280 . The desired lash therefore is now fixed. It will be appreciated that other configurations may be employed for fixing the bearing axle  280  relative to the inner rocker arm  222  once the desired lash is set. While the above bearing axle  280  has been described as part of a switching rocker arm  210 , the same principals may be used in standard rocker arms. 
     The foregoing description of the examples has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular example are generally not limited to that particular example, but, where applicable, are interchangeable and can be used in a selected example, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.