Abstract:
A rocker arm for engaging a cam is disclosed. An outer arm and inner arm are configured to transfer motion to a valve of an internal combustion engine. A latching mechanism includes a latch, sleeve and orientation member. The sleeve engages the latch and a bore in the inner arm, and also provides an opening for an orientation member used in providing the correct orientation for the latch with respect to the sleeve and the inner arm. The sleeve, latch and inner arm have reference marks used to determine the optimal orientation for the latch.

Description:
PRIORITY 
     This application claims priority to U.S. Provisional Application No. 61/315,464, filed Mar. 19, 2010. The entirety of that application is incorporated herein. 
    
    
     FIELD OF THE INVENTION 
     This application is directed to switching rocker arms for internal combustion engines. 
     BACKGROUND 
     Switching rocker arms allow for control of valve actuation by alternating between two or more states, usually involving multiple arms, such as in inner arm and outer arm. In some circumstances, these arms 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. 
     SUMMARY 
     A rocker arm for engaging a cam is disclosed. An outer arm and inner arm are configured to transfer motion to a valve of an internal combustion engine. A latching mechanism includes a latch, sleeve and orientation member. The sleeve engages the latch and a bore in the inner arm, and also provides an opening for an orientation member used in providing the correct orientation for the latch with respect to the sleeve and the inner arm. The sleeve, latch and inner arm have reference marks used to determine the optimal orientation for the latch. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       It will be appreciated that the illustrated boundaries of elements in the drawings represent only one example of the boundaries. One of ordinary skill in the art will appreciate that a single element may be designed as multiple elements or that multiple elements may be designed as a single element. An element shown as an internal feature may be implemented as an external feature and vice versa. 
       Further, in the accompanying drawings and description that follow, like parts are indicated throughout the drawings and description with the same reference numerals, respectively. The figures may not be drawn to scale and the proportions of certain parts have been exaggerated for convenience of illustration. 
         FIG. 1  illustrates a perspective view of an exemplary switching rocker arm  100  as it may be configured during operation with a three lobed cam  102 . 
         FIG. 2  illustrates a perspective view of an exemplary switching rocker arm  100 . 
         FIG. 3  illustrates another perspective view of an exemplary switching rocker arm  100 . 
         FIG. 4  illustrates an exploded view of an exemplary switching rocker arm  100 . 
         FIG. 5  illustrates a top-down view of exemplary switching rocker arm  100 . 
         FIG. 6  illustrates a cross-section view taken along line  6 - 6  in  FIG. 5 . 
         FIG. 7  illustrates a cross-sectional view of the latching mechanism  201  in its latched state along the line  7 - 7  in  FIG. 5 . 
         FIG. 8  illustrates a cross-sectional view of the latching mechanism  201  in its unlatched state. 
         FIGS. 9A-9F  illustrate several retention devices for orientation pin  221 . 
         FIG. 10  illustrates an exemplary latch  200 . 
         FIG. 10A  illustrates exemplary front surfaces of the latch  200 . 
         FIG. 11  illustrates an alternative latching mechanism  201 . 
         FIGS. 12-14  illustrate an exemplary method of assembling a switching rocker arm. 
         FIG. 15  illustrates an alternative embodiment of pin  1000 . 
     
    
    
     DETAILED DESCRIPTION 
     Certain terminology will be used in the following description for convenience in describing the figures will not be limiting. The terms “upward,” “downward,” and other directional terms used herein will be understood to have their normal meanings and will refer to those directions as the drawing figures are normally viewed. 
       FIGS. 1 and 2  illustrates a perspective view of an exemplary switching rocker arm  100  as it may be configured during operation with a three lobed cam  102 , a lash adjuster  110 , valve  112 , spring  114  and spring retainer  116 . The cam  102  has a first and second high-lift lobe  104 ,  106  and a low lift lobe  108 . The switching rocker arm has an outer arm  120  and an inner arm  122 . During operation, the high lift lobes  104 ,  106  contact the outer arm  120  while the low lift lobe contacts the inner arm  122 . The lobes cause periodic downward movement of the outer arm  120  and inner arm  122 . The downward motion is transferred to the valve  112  by inner arm  122 , thereby opening the valve. Rocker arm  100  is switchable between a high lift mode to low lift mode. In the high lift mode, the outer arm  120  is latched to the inner arm  122 . During engine operation, the high lift lobes periodically push the outer arm  120  downward. Because the outer arm  120  is latched to the inner arm  122 , the high lift motion is transferred from outer arm  120  to inner arm  122  and further to the valve  112 . When the rocker arm  100  is in its unswitched mode, the outer arm  120  is not latched to the inner arm  122 , and so high lift movement exhibited by the outer arm  120  is not transferred to the inner arm  122 . Instead, the low lift lobe contacts the inner arm  122  and generates low lift motion that is transferred to the valve  112 . When unlatched from inner arm  122 , the outer arm  120  pivots about axle  118 , but does not transfer motion to valve  112 . 
       FIG. 2  illustrates a perspective view of an exemplary switching rocker arm  100 . The switching rocker arm  100  is shown by way of example only and it will be appreciated that the configuration of the switching rocker arm  100  that is the subject of this disclosure is not limited to the configuration of the switching rocker arm  100  illustrated in the figures contained herein. 
     As shown in  FIG. 2 , the switching rocker arm  100  includes an outer arm  120  having a first outer side arm  124  and a second outer side arm  126 . An inner arm  122  is disposed between the first outer side arm  124  and second outer side arm  126 . The inner arm  122  and outer arm  120  are both mounted to a pivot axle  118 , located adjacent the first end  101  of the rocker arm  100 , which secures the inner arm  122  to the outer arm  120  while also allowing a rotational degree of freedom about the pivot axle  118  of the inner arm  122  with respect to the outer arm  120 . In addition to the illustrated embodiment having a separate pivot axle  118  mounted to the outer arm  120  and inner arm  122 , the pivot axle  118  may be part of the outer arm  120  or the inner arm  122 . 
     The rocker arm  100  illustrated in  FIG. 2  has a roller  128  that is configured to engage a central low-lift lobe of a three-lobed cam. First and second slider pads  130 ,  132  of outer arm  120  are configured to engage the first and second high-lift lobes  104 ,  106  shown in  FIG. 1 . First and second torsion springs  134 ,  136  function to bias the outer arm  120  upwardly after being displaced by the high lift lobes  104 ,  106 . First and second over-travel limiters  140 ,  142  prevent over-coiling of the torsion springs  134 ,  136  and exceeding the stress capability of the springs  134 ,  136 . The over-travel limiters  140 ,  142  contact the first and second oil gallery  144 ,  146  when the outer arm  120  reaches its maximum rotation during low-lift mode. At this point, the interference between the over-travel limiters  140 ,  142  and the galleries  144 ,  146  stops any further downward rotation of the outer arm  120 . 
       FIG. 3  illustrates another perspective view of the rocker arm  100 . A first clamping lobe  150  protrudes from underneath the first slider pad  130 . A second clamping lobe (not shown) is similarly placed underneath the second slider pad  132 . During the manufacturing process, clamping lobes  150  are engaged by clamps during grinding of the slider pads  130 ,  132 . Grinding of these surfaces requires that the pads  130 ,  132  remain parallel to one another and that the outer arm  120  not be distorted. Clamping at the clamping lobes  150  prevents distortion that may occur to the outer arm  120  under other clamping arrangements. For example, clamping at the clamping lobe  150 , which are preferably integral to the outer arm  120 , assist in eliminating any mechanical stress that may occur by clamping that squeezes outer side arms  124 ,  126  toward one another. In another example, the location of clamping lobe  150  immediately underneath slider pads  130 ,  132 , results in substantially zero to minimal torque on the outer arm  120  caused by contact forces with the grinding machine. In certain applications, it may be necessary to apply pressure to other portions in outer arm  120  in order to minimize distortion. 
       FIG. 4  illustrates an exploded view of the switching rocker arm  100  of  FIGS. 2 and 3 . As shown in  FIG. 4 , when assembled, roller  128  is part of a needle roller-type assembly  129 , having needles  180  mounted between the roller  128  and roller axle  182 . Roller axle  182  is mounted to the inner arm  122  via roller axle apertures  183 ,  184 . Roller assembly  129  serves to transfer the rotational motion of the low-lift cam  108  to the inner rocker arm  120 , and in turn transfer motion to the valve  112  in the unlatched state. Pivot axle  118  is mounted to inner arm  122  through collar  123  and to outer arm  120  through pivot axle apertures  160 ,  162  at the first end  101  of rocker arm  100 . Lost motion rotation of the outer arm  120  relative to the inner arm  122  in the unlatched state occurs about pivot axle  118 . Lost motion movement in this context means movement of the outer arm  120  relative to the inner arm  122  in the unlatched state. This motion does not transmit the rotating motion of the first and second high-lift lobe  104 ,  106  of the cam  102  to the valve  112  in the unlatched state. 
     Other configurations other than the roller assembly  129  and pads  130 ,  132  also permit the transfer of motion from cam  102  to rocker arm  100 . For example, a smooth non-rotating surface (not shown) such as pads  130 ,  132  may be placed on inner arm  122  to engage low-lift lobe  108 , and roller assemblies may be mounted to rocker arm  100  to transfer motion from high-lift lobes  104 ,  106  to outer arm  120  of rocker arm  100 . 
     The mechanism  201  for latching inner arm  122  to outer arm  120 , which in the illustrated embodiment is found near second end  103  of rocker arm  100 , is shown in  FIG. 4  as comprising latch pin  200 , collar  210 , orientation pin  221 , and latch spring  230 . The mechanism  201  is configured to be mounted inside inner arm  122  within bore  240 . As explained below, in the assembled rocker arm  100  latch  200  is extended in high-lift mode, securing inner arm  122  to outer arm  120 . In low-lift mode, latch  200  is retracted into inner arm  122 , allowing lost motion movement of outer arm  120 . Oil pressure provided through the first and second oil gallery  144 ,  146 , which may be controlled, for example, by a solenoid, controls whether latch  200  is latched or unlatched. Plugs  170  are inserted into gallery holes  172  to form a pressure tight seal closing first and second oil gallery  144 ,  146  and allowing them to pass oil to latching mechanism  201 . 
       FIG. 5  illustrates a top-down view of rocker arm  100 . As shown in  FIG. 5 , over-travel limiters  140 ,  142  extend from outer arm  120  toward inner arm  122  to overlap with galleries  144 ,  146 , ensuring interference between limiters  140 ,  142  and galleries  144 ,  146 . As shown in  FIG. 6 , representing a cross-section view taken along line  6 - 6 , contacting surface  143  of limiter  140  is contoured to match the cross-sectional shape of gallery  144 . This assists in applying even distribution of force when limiters  140 ,  142  make contact with galleries  144 ,  146 . 
       FIG. 7  illustrates a cross-sectional view of the latching mechanism  201  in its latched state along the line  7 - 7  in  FIG. 5 . A latch  200  is disposed within bore  240 . Latch  200  has a spring bore  202  in which biasing spring  230  is inserted. The latch  200  has a rear surface  203  and a front surface  204 . Latch  200  also has a first generally cylindrical surface  205  and a second generally cylindrical surface  206 . The latch  200  extends along a longitudinal latch axis  200   a . First generally cylindrical surface  205  has a diameter larger than that of the second generally cylindrical surface  206 . Spring bore  202  is generally concentric with surfaces  205 ,  206 . 
     Sleeve  210  has a generally cylindrical outer surface  211  that interfaces a first generally cylindrical bore wall  241 , and a generally cylindrical inner surface  215 . Bore  240  has a first generally cylindrical bore wall  241 , and a second generally cylindrical bore wall  242  having a larger diameter than first generally cylindrical bore wall  241 . The generally cylindrical outer surface  211  of sleeve  210  and first generally cylindrical surface  205  of latch  200  engage first generally cylindrical bore wall  241  to form pressure tight seals. Further, the generally cylindrical inner surface  215  of sleeve  210  also forms a pressure tight seal with second generally cylindrical surface  206  of latch  200 . These seals allow oil pressure to build in volume  250 , which encircles second generally cylindrical surface  206  of latch  200 . 
     The default position of latch  200 , shown in  FIG. 7 , is the latched position. Spring  230  biases latch  200  outwardly from bore  240  into the latched position. Oil pressure applied to volume  250  retracts latch  200  and moves it into the unlatched position ( FIG. 8 ). Other configurations are also possible, such as where spring  230  biases latch  200  in the unlatched position, and application of oil pressure between bore wall  208  and rear surface  203  causes latch  200  to extend outwardly from the bore  240  to latch outer arm  120 . 
     In the latched state, latch  200  engages a latch engages surface  214  of outer arm  120  with arm engaging surface  213 . As shown in  FIG. 7 , outer arm  120  is impeded from moving downward and will transfer motion to inner arm  122  through latch  200 . An orientation feature  212  takes the form of a channel into which orientation pin  221  extends from outside inner arm  122  through first pin opening  217  and then through second pin opening  218  in sleeve  210 . The orientation pin  221  extends along a longitudinal orientation pin axis  221   a  that is generally transverse to the longitudinal latch axis  200   a . The orientation pin  221  is generally solid and smooth. A retainer  222  secures pin  221  in place. The orientation pin  221  prevents excessive rotation of latch  200  around the longitudinal latch axis  207  within bore  240 . 
     As can be seen in  FIG. 8 , upon introduction of pressurized oil into volume  250 , latch  200  retracts into bore  240 , allowing outer arm  120  to undergo lost motion rotation with respect to inner arm  122 . The outer arm  120  is then no longer impeded by latch  200  from moving downward and exhibiting lost motion movement. Pressurized oil is introduced into volume  250  through oil opening  280 , which is in fluid communication with oil galleries  144 ,  146 . As latch  200  retracts, it encounters bore wall  208  with its rear surface  203 . In one preferred embodiment, rear surface  203  of latch  200  has a flat annular or sealing surface  207  that lies generally perpendicular to first and second generally cylindrical bore wall  241 ,  242 , and parallel to bore wall  208 . The flat annular surface  207  forms a seal against bore wall  208 , which reduces oil leakage from volume  250  through the seal formed by first generally cylindrical surface  205  of latch  200  and first generally cylindrical bore wall  241 . 
       FIGS. 9A-9F  illustrate several retention devices for orientation pin  221 . In  FIG. 9A , pin  221  is cylindrical with a uniform thickness. A push-on ring  910 , as shown in  FIG. 9C  is located in recess  224  located in sleeve  210 . Pin  221  is inserted into ring  910 , causing teeth  912  to deform and secure pin  221  to ring  910 . Pin  221  is then secured in place due to the ring  910  being enclosed within recess  224  by inner arm  122 . In another embodiment, shown in  FIG. 9B , pin  221  has a slot  902  in which teeth  912  of ring  910  press, securing ring  910  to pin  221 . In another embodiment shown in  FIG. 9D , pin  221  has a slot  904  in which an E-styled clip  914  of the kind shown in  FIG. 9E , or a bowed E-styled clip  914  as shown in  FIG. 9F  may be inserted to secure pin  221  in place with respect to inner arm  122 . In yet other embodiments, wire rings may be used in lieu of stamped rings. During assembly, the E-styled clip  914  is placed in recess  224 , at which point the sleeve  210  is inserted into inner arm  122 , then, the orientation pin  221  is inserted through the clip  910 . 
     An exemplary latch  200  is shown in  FIG. 10 . The latch  200  is generally divided into a head portion  290  and a body portion  292 . The front surface  204  is a protruding convex curved surface. This surface shape extends toward outer arm  120  and results in an increased chance of proper engagement of arm engaging surface  213  of latch  200  with outer arm  120 . Arm engaging surface  213  comprises a generally flat surface. Arm engaging surface  213  extends from a first boundary  285  with second generally cylindrical surface  206  to a second boundary  286 , and from a boundary  287  with the front surface to a boundary  233  with surface  232 . The portion of arm engaging surface  213  that extends furthest from surface  232  in the direction of the longitudinal axis A of latch  200  is located substantially equidistant between first boundary  285  and second boundary  286 . Conversely, the portion of arm engaging surface  213  that extends the least from surface  232  in the axial direction A is located substantially at first and second boundaries  285 ,  286 . As shown in  FIG. 10   a , front surface  204  need not be a convex curved surface (solid line  204   a ) but instead can be an angled or v-shaped surface (phantom line  204   b ) or some other shape. The arrangement permits greater rotation of the latch  200  within bore  240  while improving the likelihood of proper engagement of arm engaging surface  213  of latch  200  with outer arm  120 . 
     An alternative latching mechanism  201  is shown in  FIG. 11 . An orientation plug  1000 , in the form of a hollow cup-shaped plug, is press-fit into sleeve hole  1002  and orients latch  200  by extending into orientation feature  212 , preventing latch  200  from rotating excessively with respect to sleeve  210 . As discussed further below, an aligning slot  1004  assists in orienting the latch  200  within sleeve  210  and ultimately within inner arm  122  by providing a feature by which latch  200  may be rotated within the sleeve  210 . The alignment slot  1004  may serve as a feature with which to rotate the latch  200 , and also to measure its relative orientation. 
     With reference to  FIGS. 12-14 , an exemplary method of assembling a switching rocker arm  100  is as follows: The orientation plug is press-fit into sleeve hole  1002  and latch  200  is inserted into generally cylindrical inner surface  215  of sleeve  210 . The latch  200  is then rotated clockwise until orientation feature  212  reaches plug  1000 , at which point interference between the orientation feature  212  and plug  1000  prevents further rotation. An angle measurement A 1 , as shown in  FIG. 12 , is then taken corresponding to the angle between arm engaging surface  213  and sleeve references  1010 ,  1012 , which are aligned to be perpendicular to sleeve hole  1002 . Aligning slot  1004  may also serve as a reference line for latch  200 , and key slots  1014  may also serve as references located on sleeve  210 . The latch  200  is then rotated counterclockwise until orientation feature  212  reaches plug  1000 , preventing further rotation. As seen in  FIG. 13 , a second angle measurement A 2  is taken corresponding to the angle between arm engaging surface  213  and sleeve references  1010 ,  1012 . Rotating counterclockwise and then clockwise is also permissible in order to obtain A 1  and A 2 . As shown in  FIG. 14 , upon insertion into the inner arm  122 , the sleeve  210  and pin subassembly  1200  is rotated by an angle A as measured between inner arm references  1020  and sleeve references  1010 ,  1012 , resulting in the arm engaging surface  213  being oriented horizontally with respect to inner arm  122 , as indicated by inner arm references  1020 . The amount of rotation A should be chosen to maximize the likelihood the latch  200  will engage outer arm  120 . One such example is to rotate subassembly  1200  an angle half of the difference of A 2  and A 1  as measured from inner arm references  1020 . Other amounts of adjustment A are possible within the scope of the present disclosure. 
     A profile of an alternative embodiment of pin  1000  is shown in  FIG. 15 . Here, the pin  1000  is hollow, partially enclosing an inner volume  1015 . The pin has a substantially cylindrical first wall  1030  and a substantially cylindrical second wall  1040 . The substantially cylindrical first wall  1030  has a diameter D 1  larger than diameter D 2  of second wall  1040 . A flange  1025  ensures orientation pin  1000  will not be displaced downwardly through pin opening  218  in sleeve  210 . 
     For the purposes of this disclosure and unless otherwise specified, “a” or “an” means “one or more.” To the extent that the term “includes” or “including” is used in the specification or the claims, it is intended to be inclusive in a manner similar to the term “comprising” as that term is interpreted when employed as a transitional word in a claim. Furthermore, to the extent that the term “or” is employed (e.g., A or B) it is intended to mean “A or B or both.” When the applicants intend to indicate “only A or B but not both” then the term “only A or B but not both” will be employed. Thus, use of the term “or” herein is the inclusive, and not the exclusive use. See, Bryan A. Garner, A Dictionary of Modern Legal Usage 624 (2d. Ed. 1995). Also, to the extent that the terms “in” or “into” are used in the specification or the claims, it is intended to additionally mean “on” or “onto.” Furthermore, to the extent the term “connect” is used in the specification or claims, it is intended to mean not only “directly connected to,” but also “indirectly connected to” such as connected through another component or multiple components. As used herein, “about” will be understood by persons of ordinary skill in the art and will vary to some extent depending upon the context in which it is used. If there are uses of the term which are not clear to persons of ordinary skill in the art, given the context in which it is used, “about” will mean up to plus or minus 10% of the particular term. From about X to Y is intended to mean from about X to about Y, where X and Y are the specified values. 
     While the present disclosure illustrates various embodiments, and while these embodiments have been described in some detail, it is not the intention of the applicant to restrict or in any way limit the scope of the claimed invention to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the invention, in its broader aspects, is not limited to the specific details and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of the applicant&#39;s claimed invention. Moreover, the foregoing embodiments are illustrative, and no single feature or element is essential to all possible combinations that may be claimed in this or a later application.