Abstract:
A poppet valve operating system for an internal combustion engine includes a finger follower which is driven by an intermediate rocker. The intermediate rocker selectively converts motion imparted by a drive cam into either a purely translational trajectory, or into a mixed translational and rotational trajectory, so as to open a poppet valve which is ultimately actuated by a finger follower interposed between the intermediate rocker and the valve.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a system for operating poppet-type cylinder valves of a reciprocating internal combustion engine, so as to selectively control the duration of the valve opening events. 
   2. Disclosure Information 
   Variable valve duration control devices have been the subject of much invention during the past few decades. U.S. Pat. No. 5,373,818 discloses but one example of such inventive activity. The &#39;818 patent describes a variable duration valve operating system having at least one embodiment which is useful with bucket tappets, but which is not useful for application to roller finger followers. A second embodiment may be employed with a finger follower, but in the context of an operating system having high inertia, and therefore, unacceptably slow system response time. 
   Other types of variable valve operating devices have been used, including such systems as axially shiftable camshafts, cam timing control devices, electromagnetically actuated valves, and yet other devices. The present system is readily usable with finger follower valve actuation systems and allows the control of valve events extending from no valve opening whatsoever (i.e., valve deactivation) to a maximum opening. 
   SUMMARY OF THE INVENTION 
   A poppet valve operating system for an internal combustion engine includes a poppet valve, a finger follower for actuating the poppet valve, and an intermediate rocker for actuating a finger follower. The intermediate rocker has a control surface formed therein. A drive cam, powered by a crankshaft of the engine, actuates the intermediate rocker by providing input force tending to move the intermediate rocker translationally. A selectively positioned control roller which bears upon the control surface of the intermediate rocker controls the lift of the poppet valve by selectively causing the motion of the intermediate rocker to be at least partially rotational. The control roller is positionable such that the intermediate rocker has a range of movement extending from purely translational movement, which does not cause the finger follower to lift the poppet valve, to a range of mixed translational and rotational trajectories causing the finger follower to lift the poppet valve to varying degrees. The finger follower has a first end contacting the poppet valve, and a second end operatively connected with a hydraulic lash adjuster extending between a cylinder head of the engine and the second end of the finger follower. 
   According to another aspect of the present invention, a method for operating a poppet cylinder valve in an internal combustion engine includes the steps of providing a drive cam powered by a crankshaft to the engine, providing an intermediate rocker actuated by the drive cam, and providing a finger follower for actuating a poppet valve, with the finger follower being actuated by the intermediate rocker. Finally, the present method includes the step of providing a control roller for interacting with a control surface incorporated as part of the intermediate rocker, so as to determine the lift of a poppet valve actuated by the finger follower by controlling the rotational movement of the intermediate rocker resulting from actuation of the intermediate rocker by the drive cam. 
   The previously described control roller has a number of operating positions including at least a first position in which the intermediate rocker moves purely translationally, and a second position, in which the intermediate rocker moves both translationally and rotationally. 
   The present valve operating system offers the advantage of lower operating inertia as compared with known designs, as well as smaller package volume. Further, the present system may be employed with roller finger follower technology. 
   Other advantages, as well as objects and features of the present invention, will become apparent to the reader of this specification. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side elevation of a cylinder valve operating system according to the present invention with the system&#39;s drive cam on its base circle. 
       FIG. 2  shows the system of  FIG. 1 , but with the drive cam,  40 , rotated 90 degrees from the midpoint of the cam&#39;s base circle. 
       FIG. 3  is similar to  FIGS. 1 and 2 , but shows drive cam  40  rotated to its maximum lift position. 
       FIG. 4  illustrates the system of  FIGS. 1–3 , but in a lower valve lift position, and with drive cam  40  being in its base circle location. 
       FIG. 5  illustrates the set-up of  FIG. 4 , but with drive cam  40  in an intermediate position. 
       FIG. 6  illustrates the set-up of  FIGS. 4–5 , but with drive cam  40  in a maximum lift position. 
       FIG. 7  illustrates the present system with drive cam  40  in a maximum lift position, but with the system producing no lift at valve  14 . 
       FIG. 8  is an elevational view of the present system, partially broken away, taken along the line of  8 — 8  of  FIG. 1 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   As shown in various figures, the present cylinder valve operating system,  10 , is intended for use with poppet valves  14 , which are mounted within cylinder head  18  of an engine. Valves  14  are returned to their closed positions by means of valve springs  16 . Each of valves  14  is actuated by means of a finger follower,  20 , which has a first end in contact with valve  14  and a second end in contact with lash adjuster  28 , which is mounted to cylinder head  18 . Finger follower  20  has a roller,  24 , which contacts intermediate rocker  30 . 
   Intermediate rocker  30  is biased into contact with drive cam  40  by means of compression spring  62 . Alternatively, a torsion spring (not shown) could be used for this purpose. Intermediate rocker  30  rotatably actuates finger follower  20  as drive cam  40 , which is mounted upon camshaft  44 , and driven either by a crankshaft or other rotating member of the engine (not shown), pushes upon rocker roller  32 , thereby moving intermediate rocker  30  translationally. Camshaft  44  and intermediate rocker  30  are mounted so that the motion imparted by camshaft  44  and drive cam  40  to intermediate rocker  30  is purely translational. This translational movement is controllably transformed into rotational movement of intermediate rocker  30  by control roller  48 , which is mounted upon support shaft  50 . In essence, intermediate rocker  30  pivots about an instantaneous contact point existing between control surface  34  and the outer diametral surface of control shaft  58 . Support shaft  50  is carried within control slot  54  formed in cylinder head  18   c . Alternatively, support shaft  50  may be carried within a slotted member rigidly attached to cylinder head  18 . 
   Control slot  54  permits translational movement of support shaft  50 . This translational movement is produced by control cam  56  which is mounted upon control shaft  58 . As control shaft  58  is rotated, control cam  56  displaces control shaft  50  within slot  54 , so as to move control roller  48  to a new operating position. In general, when control roller  48  is moved closer to camshaft  44 , valve lift will be increased because control roller  48  will be operating on rocker ramp  34 , which is a control surface formed in intermediate rocker  30 , in a position so that the motion depicted in  FIGS. 3 and 6  will occur. 
     FIGS. 1 and 4  show valve  14  in its closed position, with drive cam  40  on its based circle, or no lift, position. Thus, valve  14  is closed in  FIGS. 1 and 4 . However, in  FIGS. 2 and 5 , drive cam  40  has rotated to a mid-lift position and in  FIG. 2 , valve  14  has started to lift. Note however, that in  FIG. 5 , valve  14  has not begun to lift because control roller  48  is not bearing upon a portion of rocker ramp  34  wherein intermediate rocker  30  has started to move through a trajectory in which it not only translates as indicated, but also rotates as shown in  FIG. 2 , but not in  FIG. 5 . In  FIGS. 3 and 6 , drive cam  40  has rotated to its maximum lift position. It is noted however that the lift imparted to valve  14  is greater in  FIG. 3  than that depicted in  FIG. 6 . This is easily understood by virtue of the positions shown for control roller  48  in  FIGS. 3 and 6 . Note that in  FIG. 3 , control roller  48  is much higher up on the ramp or control surface  34  of intermediate rocker  30 . 
   In  FIG. 7 , the present system is at position of maximum lift of drive cam  40 , but valve  14  remains closed because control roller  48  is on the base portion of rocker ramp  34  which simulates the base circle of a conventional rotating cam lobe. In other words, no lift occurs because notwithstanding that translational motion of intermediate rocker  30  has occurred and, to the same extent as it always occurs with this system, intermediate rocker has not been caused to rotate at all, with the result being that valve  14  remains closed. Accordingly, the present system may be employed to produce a full range of valve lifts extending from no lift whatsoever to a maximum lift value, depending upon the geometry of rocker ramp  34 , as well as the lift available from drive cam  40 . 
     FIG. 8  shows the present system as driving multiple valves,  14 , which could comprise either intake valves or exhaust valves. This view more clearly shows the spatial orientation of control shaft  58 , intermediate rocker  30 , and finger follower  20 . 
   Although the present invention has been described in connection with particular embodiments thereof, it is to be understood that various modifications, alterations, and adaptations may be made by those skilled in the art without departing from the spirit and scope of the invention set forth in the following claims.