Abstract:
In an internal combustion engine using poppet type valves, a center pivot rocker arm is moved through a specific path wherein the roller in contact with a cam is moved to alter the phasing of the valves or injectors in the engine. Depending on the interface between the valve or injector and the rocker arm, the rocker ratio of the rocker arm may be altered, giving a change in lift as well. By positioning a control arm at desired points on either side of a centered position, and rotating the control arm about its own pivot point via an arm actuator, phase change is achieved. The arm actuator controls the location of the control arm and thus the timing of the valve or injector relative to the rotation of the cam. Advanced, centered, and retarded phase change is possible depending upon the movement of the control arm.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application is a divisional application of application Ser. No. 12/247,105 filed on Oct. 7, 2008 titled “Varying The Phase And Lift Of A Rocker Arm On A Camshaft Actuating A Valve Or Injector” which is incorporated herein by reference in its entirety for all that is taught and disclosed therein. This application is also related to co-pending application Ser. No. 12/247,105 filed on Oct. 7, 2008 titled “Varying The Phase And Lift Of A Rocker Arm On A Camshaft Actuating A Valve Or Injector” by the same inventor of this invention. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to an internal combustion engine using poppet type valves to direct gases into and out of one or more cylinders or cam operated fuel injection units to inject fuel into one or more cylinders. More particularly, a rocker arm is moved through a specific path wherein the roller in contact with a cam is moved to alter the phasing of the valves or injectors in the engine. Depending on the interface between the valve or injector and the rocker arm the rocker ratio of the rocker arm may be altered, giving a change in lift as well. 
     BACKGROUND OF THE INVENTION 
     Variable valve timing can be achieved by numerous methods. A description of a phasing system for roller lifter followers on a camshaft is given by Riley in U.S. Pat. No. 6,155,216, which is hereby incorporated by reference for all that is taught and disclosed therein. Variable cam timing, wherein the cam lobe is rotated relative to crank timing is given by Hampton in U.S. Pat. No. 4,754,727. This approach, of rotating the camshaft relative to the cam sprocket, is used by many engine manufacturers. 
     An alternative method is to move the rocker arm, with follower relative to the cam, as in U.S. Pat. No. 5,572,962 by Riley. In this case the phasing is achieved via a gearing system whereby the pivot shaft is moveable in a way that ties the change of phase to changes in lift and duration. 
     SUMMARY OF THE INVENTION 
     The present invention describes a system for providing controlled phasing in one embodiment (shown in  FIGS. 1 ,  2 A,  2 B,  2 C,  5 A, and  5 B), and controlled phasing with lift change in an alternative embodiment (shown in  FIGS. 4 ,  6 A,  6 B, and  6 C) of a center pivot rocker arm with a roller in contact with a cam. An alternate embodiment of providing the controlled movement path is shown in  FIGS. 7A ,  7 B,  8 A, and  8 B. 
     One constraint in moving a rocker arm to change phase is that the height of the rocker arm tip on the valve stem or injector button must remain nearly constant, that is, within a very small, or minimal, range of vertical displacement. Another constraint is that the contact point between the rocker arm and the axis of the valve or injector will vary during actuation. 
     Allowing the roller of the rocker arm to move in an arc about the center of the cam (while maintaining contact with the base circle and the other end of the rocker maintaining contact with the valve stem or actuator button) results in the pivot shaft of the rocker arm describing its own arc. In most instances this rocker arm arc will be substantially circular. Allowing the path of the pivot shaft center to pivot about the center of that circle will deliver a phase change between the cam and the valve or injector with insignificant or minimal change in height of the contact point between the rocker arm tip and the valve stem or injector button, or a bridge acting on two valves. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  shows an isometric view of a cam, rocker arm, valve or injector, and a pivot shaft for the rocker arm being carried by a separate pivoting mechanism. 
         FIG. 1B  shows an alternate embodiment that utilizes a rotational actuator. 
         FIG. 2A  shows a side-on view of the same mechanism as in  FIG. 1A , with the rocker arm in a position of advanced timing. 
         FIG. 2B  shows a side-on view of the same mechanism as in  FIG. 1A , with the rocker arm in a position of centered timing. 
         FIG. 2C  shows a side-on view of the same mechanism as in  FIG. 1A , with the rocker arm in a position of retarded timing. 
         FIG. 3  shows an example plot of the minimal change in rocker arm tip height as the rocker arm is phased through its range. 
         FIG. 4  shows the same overall geometry as in  FIG. 2 , with the exception that the elephant&#39;s foot contactor between the rocker arm and the valve or injector is now located on the valve or injector. The underside of the rocker arm adjuster tip is flat. 
         FIG. 5A  shows an isometric view of the mechanism of  FIG. 1A , but with the rocker arm actuating two valves via a bridge. 
         FIG. 5B  shows a detailed view of the elephant&#39;s foot and the slot into which it fits in the bridge. 
         FIG. 6A  shows the same general view of a rocker arm acting on a bridge for two valves as in  FIGS. 5A and 5B , but with the elephant&#39;s foot attached to the bridge. 
         FIG. 6B  shows a detailed view of the elephant&#39;s foot mounted to the bridge. 
         FIG. 6C  shows a detailed view of the underside of the bridge with a retaining cap to capture the valve tip. 
         FIG. 7A  shows an isometric view similar to  FIG. 1A  but where the circular movement path of the pivot shaft is determined by the shaped underside of a fixed cap, with the pivot shaft in contact with the cap. 
         FIG. 7B  shows a similar configuration to  FIG. 7A  but with a load bearing member inserted between the pivot shaft and cap with the circular underside. 
         FIG. 8A  shows a side view of the geometry in  FIG. 7A , with the pivot shaft cap of the appropriate radius and location to allow the correct pivot shaft movement, thus maintaining rocker arm tip height to a minimal change. 
         FIG. 8B  shows a side view to  FIG. 7B  with a load distributing member between the pivot shaft and cap. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the Figures, in which like reference numerals refer to like components thereof,  FIG. 1A  shows an isometric view of a cam, rocker arm, valve or injector, and a pivot shaft for the rocker arm being carried by a separate pivoting mechanism. Though only one rocker arm, valve or injector, roller, control arm, and arm actuator are shown in  FIG. 1A , one skilled in the art will recognize that two, three, four, or more sets of the same may be employed in any given engine. 
     In a conventional, center-pivot rocker arm for an overhead cam layout, pivot shaft  1  is in a fixed location, and rocker arm  2  pivots about this fixed location. Cam  3  attached to camshaft  37  acts on roller  4  (the roller  4  can be replaced by a curved sliding surface) to displace rocker arm  2 . Curved arrow  9  indicates the direction of rotation of cam  3 . The elephant&#39;s foot  5  attached to the tip of rocker arm  2  pushes down on valve or injector  6 . The tip of rocker arm  2  usually has a mechanical or hydraulic lash adjuster which is not required to explain the function of the current invention, and is not shown. Valve or injector  6  is usually spring loaded (spring not shown) to return same to its original position as cam  3  returns to its base circle. 
     Phase change is achieved in this invention by moving pivot shaft  1  through a circular arc centered about pivot axis  8  of shaft  38  fixed to control arm  7 . In this embodiment this is shown by positioning control arm  7  at desired points on either side of a centered position, rotating control arm  7  about its own pivot axis  8  of shaft  38  via an arm actuator  10 . Thus, in this embodiment, pivot shaft  1  is no longer fixed. Arm actuator  10  controls the location of control arm  7  by being able to vary its length from its actuator axis  11 , and thus the timing of the valve or injector  6  relative to the rotation of cam  3  is changed. Arm actuator  10  may be a hydraulic actuator, a ball lead screw powered by an electric motor, which could be a stepper motor, or another type of rotary or linear actuator. In another embodiment shown in  FIG. 1B , a rotating actuator  39  is attached to shaft  38  and rotates shaft  38  clockwise and counterclockwise in order to vary the phase. 
       FIG. 2A  shows a side-on view of the mechanism in  FIG. 1A  with control arm  7  located in an advanced position from a centered position (arm actuator  10  and actuator axis  11  are not shown in this view). If pivot shaft  1  were held fixed (with a suitable locating mechanism in place of control arm  7 ) in a centered position this would correspond to a conventional design without variable timing. Dashed line  12  indicates the location of the centered timing position with roller  4  contacting cam  3  when on the base circle of the cam, which represents a zero phase change. Dashed line  13  indicates advanced timing (advanced phase change) and dashed line  14  indicates retarded timing (retarded phase change). Corresponding to these different timing indicators, dashed line  15  indicates control arm  7  in the centered position (zero phase position), dashed line  16  indicates the control arm  7  in the advanced phase position, and dashed line  17  indicates the control arm  7  in the retarded phase position. 
       FIG. 2B  and  FIG. 2C  show the location of components in the centered and retarded positions respectively (arm actuator  10  and actuator axis  11  are not shown in these views). The angular movement required for the cam  3  to roller  4  phasing will be different for the angular movement required for different positions of control arm  7 . Please note the change in position of elephant&#39;s foot  5  with respect to the valve or injector  6  in each of the three views. 
       FIG. 3  shows a plot of the minimal change in height of the rocker arm tip throughout a selected range of phasing of the mechanism. Since there is only a very small height change of the rocker arm tip as the rocker arm moves through its phasing path, the valve and injector height remain essentially constant during the phasing movement when cam  3  is on the base circle of the cam. Movement from the retarded position to the advanced position is approximately between about −10° to +10° or any range there between. The minimal change in height of the rocker arm tip is approximately between −0.001″ to +0.001″. Changes of movement more than −10° to +10° or changes of rocker arm tip height of more than −0.001″ to +0.001″ are within the scope of this invention, and the ranges listed are just those that have produced good results, but other ranges may also be acceptable. 
       FIG. 4  shows in an alternate embodiment a side-on view of the mechanism in a centered position, but with the elephant&#39;s foot  5 ′ now attached to the valve or injector  6  instead of rocker arm  2 ′ as shown in  FIGS. 2A ,  2 B, and  2 C. Flat surface  18  on the underside of rocker arm  2 ′ is shown as being flat. Flat surface  18  of rocker arm  2 ′ may also correspond to the bottom of a lash adjuster fitted to rocker arm  2 ′. 
       FIG. 5A  shows an isometric view of the mechanism in  FIG. 1A , but with rocker arm  2  actuating two valves or injectors  6 ′ via bridge  19 . Valves or injectors  6 ′ via bridge  19  are biased by spring  24 . Shown in greater detail in  FIG. 5B  is a suitable slot  20  shown in bridge  19  to constrain movement of elephant&#39;s foot  5  during motion of rocker arm  2 . Bridge  19  has tangs  21  that capture the end of rocker arm  2  to ensure that bridge  19  is properly constrained. 
       FIG. 6A  shows in an alternate embodiment an isometric view of the mechanism in  FIG. 4 , but with the rocker arm  2 ′ actuating two valves or injectors  6 ′ via bridge  19 ′. Flat surface  18 ′ on the underside of rocker arm  2 ′ is flat. Flat surface  18 ′ may also correspond to the bottom of a lash adjuster fitted to rocker arm  2 ′. 
       FIG. 6B  shows in greater detail the elephant&#39;s foot  5 ″ now attached to bridge  19 ′. Bridge  19 ′ has tangs  21 ′. Flat surface  18 ′ on the underside of rocker arm  2 ′ is flat. Flat surface  18 ′ may also correspond to the bottom of a lash adjuster fitted to rocker arm  2 ′. 
       FIG. 6C  shows a detailed view of the underside of the bridge  19 ′ with a recessed retaining cap  22  to capture the top of valve tip  23 . 
       FIG. 7A  shows an isometric view of similar to  FIG. 1A  but where the circular movement path of pivot shaft  1 ′ is determined by the shaped underside of curved caps  25 . In this case the pivot shaft  1 ′ is longer than pivot shaft  1  in  FIG. 1A  (and elsewhere) to allow for contact with constraining curved caps  25 . In  FIGS. 1A and 2A  (and elsewhere with the same features) control arm  7  for pivot shaft  1  is shown hinged at its pivot axis  8 . The undersides of curved caps  25  have a radius whose imaginary center corresponds to pivot axis  8  as shown in  FIG. 1A  and others. Control arm  26  has lip  36  whose geometry captures curved caps  25  on the top surface, and pivot shaft  1 ′ captures curved caps  25  on its lower surface. Thus, when arm actuator  10 ′ changes length, control arm  26  and pivot shaft  1 ′ are translated. Connector  27  joins arm actuator  10 ′ to control arm  26 . 
       FIG. 7B  shows a similar isometric view of the geometry described in  FIG. 7A  but with a load-bearing member  32  interposed between pivot shaft  1 ′ and a single piece curved cap  28 . Load-bearing member  32  allows curved cap  28  (corresponding to curved caps  25  in  FIG. 7A ) to be a single piece sitting above rocker arm  2 . Slot  29  in curved cap  28  allows control arm  30 , which is connected rigidly to load-bearing member  32  (not shown) to extend above curved cap  28  where connector  31  joins control arm  30  to arm actuator  10 ″. The underside of curved cap  28  has a radius whose imaginary center corresponds to pivot axis  8  as shown in  FIG. 1A  (and elsewhere). Load-bearing member  32  sits on pivot shaft  1 ′ and may fit snugly over pivot shaft  1 ′ so that they are clipped together. Pivot shaft  1 ′ and load-bearing member  32  are biased upwards by suitable means well know in the art (not shown) to maintain contact with curved cap  28 . 
       FIG. 8A  shows a side view of  FIG. 7A  with pivot shaft  1 ′ in contact with curved caps  25 . The circular arc movement of pivot shaft  1 ′, represented by arrow  34 , is achieved by movement of pivot shaft  1 ′ along curved surface  33  whose imaginary center of curvature corresponds to pivot axis  8  (as shown in  FIG. 1A  and elsewhere.) 
       FIG. 8B  shows a side view of  FIG. 7B . The purpose of load-bearing member  32  is to distribute the forces more controllably between pivot shaft  1 ′ and curved cap  28 , and may be useful for elevating curved cap  28  to allow for clearance between it and rocker arm  2 . Load-bearing member  32  may fit snugly over pivot shaft  1 ′ so that they are clipped together. Suitable means well known in the art are used to bias curved cap  28  to maintain contact with curved surface  35  of curved cap  28  (not shown).