Abstract:
A lobe-less cam for use in a springless poppet valve system is disclosed including a cam shaft having at least one surrounding region, at least one asymmetrical cam groove formed in the at least one surrounding region, and wherein the at least one asymmetrical cam groove has a lift portion and a descent portion.

Description:
TECHNICAL FIELD 
   The present invention relates generally to the actuation of valves in an internal combustion engine utilizing poppet valves. More specifically, the present invention relates to a lobe-less cam for the mechanical opening and closing of the valves by a camshaft/follower combination without springs. 
   BACKGROUND OF THE INVENTION 
   Conventional poppet valve systems used in four-stroke internal combustion engines are typically biased to a closed position using a spring. The valve is moved to an open position against the force of the spring by a cam or cam-actuated rocker arm. On the open stroke of the valve, the cam or rocker arm also must move the valve counter to the momentum of the valve such that the open force required is effectively doubled. These conventional poppet valve systems, however, are limited with regard to speed at which the valves can be actuated. As will be appreciated, the limit on the valve actuation speed, in turn, limits the rate at which the engine can turn (i.e., engine rpm). As engine torque and speed dictate engine power, limits on the engine rpm constrain the power of an engine. 
   In particular, increasing the actuation speed of the valve necessarily increases the force and stress applied to the components of the valve train. To compensate for the increased force and stress, the valve train components must be made stronger. Strengthening the valve train components is most often achieved by increasing the mass of the components. This increased mass, however, requires the use of a stiffer valve spring that, in turn, further increases the force and stress on the valve train components. Moreover, increasing the mass of the valve train components increases the overall reciprocating weight of the engine and, therefore, has a detrimental effect on engine performance. Thus, a balance between the stiffness of the valve spring and the mass of the valve train components limits the peak valve actuation speed of a valve train. 
   Removing the spring from the valve train alleviates the issues regarding the force need to open the valve, however, such springless valve systems are expensive to manufacture and maintain. Specifically, current springless valve systems must be manufactured and assembled to very tight tolerances in order to prevent lash or binding in the system. Additionally, during operation, because of the tight tolerances that are required, springless poppet valve systems frequently have to be adjusted resulting in increased maintenance requirements. 
   Thus, there is a need for a springless poppet valve system that overcomes the problems associated with existing poppet valve systems. 
   SUMMARY OF THE INVENTION 
   The present invention eliminates the above-mentioned needs by providing a lobe-less cam for use in a springless poppet valve system. 
   In accordance with the present invention, there is provided a lobe-less cam for use in a springless poppet valve system. The lobe-less cam includes a cam shaft having at least one surrounding region, at least one asymmetrical cam groove formed in the at least one surrounding region, and wherein the at least one asymmetrical cam groove has a lift portion and a descent portion. 
   The present invention is further directed to a springless poppet valve system including a poppet valve movable between an open position and a closed position, and a lobe-less cam having at least one asymmetrical cam groove, wherein the at least one asymmetrical cam groove accommodates a cam follower disposed to engage the lobe-less cam in the at least one asymmetrical cam groove and being operatively engaged to the poppet valve so as to move the valve from the closed position to the open position when a lift portion of the at least one asymmetrical cam groove engages the cam follower. 
   The present invention is additionally directed to a springless poppet valve system including a poppet valve movable between an open position and a closed position, a lobe-less cam having at least one asymmetrical cam groove, wherein the at least one asymmetrical cam groove accommodates a cam follower disposed to engage the lobe-less cam in the at least one asymmetrical cam groove and being operatively engaged to a rocker arm assembly, and wherein the poppet valve moves from the closed position to the open position when a lift portion of the at least one asymmetrical cam groove engages the cam follower, the cam follower operatively engaging the rocker arm assembly. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a front view of the preferred embodiment of the present invention. 
       FIG. 2  is a front view of the present invention shown in  FIG. 1  including a cam follower. 
       FIG. 3  is a side view of the present invention illustrated in  FIG. 2 . 
       FIG. 4  is a front view of the present invention shown in  FIG. 2  including a rocker arm assembly. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring now to  FIG. 1 , the preferred embodiment of the present invention is illustrated as lobe-less cam  10 . Lobe-less cam  10  includes a cam shaft  12  having at least one surrounding region  14 . Cam shaft  12  and at least one surrounding region  14  can be formed as single unitary piece. 
   At least one surrounding region  14  incorporates at least one asymmetrical cam groove  16  formed in at least one surrounding region  14 . At least one asymmetrical cam groove  16  has a lift portion  18  and a descent portion  20 . At least one asymmetrical cam groove  16  functions to accommodate a pin of a cam follower (illustrated in  FIGS. 2–4 ), with lift portion  18  and descent portion  20  serving to actuate the rising and falling movements of the cam follower, as discussed below. As a result of the use of lift portion  18  and descent portion  20 , asymmetrical cam groove  14  is ellipsoid in shape. Corresponding surrounding region  14  can be ellipsoid in shape as well, however such a shape for surrounding region  14  is not required. 
   Referring now to  FIGS. 2 and 3 , lobe-less cam  10  is illustrated in operative engagement with a cam follower  22 . Cam follower  22  incorporates a pin  24  in order to operatively engage asymmetrical cam groove  16 . Pin  24  is positioned in asymmetrical cam groove  16 , thus, as cam shaft  12  rotates about its longitudinal axis, thereby rotating asymmetrical cam groove  16 , pin  24  follows along inside asymmetrical cam groove  16 . 
   In particular, pin  24  follows rotating asymmetrical cam groove  16  into lift portion  18  and descent portion  20 . In doing so, pin  24  effectuates the raising and lowering of cam follower  22 . In operation, as cam shaft  12  rotates about its longitudinal axis, surrounding region  14  is similarly rotated, consequently rotating asymmetrical cam groove  16 . As asymmetrical cam groove  16  is rotated, pin  24  enters into lift portion  18 , causing cam follower  22  to raise in a direct relationship to the travel of pin  24  in lift portion  18 . Upon reaching the terminus of lift portion  18 , pin  24  enters descent portion  20 , causing cam follower  22  to lower in a direct relationship to the travel of pin  24  in descent portion  20 . 
   Referring now to  FIG. 4 , the preferred embodiment of the present invention is illustrated operatively engaging a rocker arm assembly  26 . 
   In operation, as cam shaft  12  rotates about its longitudinal axis, surrounding region  14  is similarly rotated, consequently rotating asymmetrical cam groove  16 . As asymmetrical cam groove  16  is rotated, pin  24  enters into lift portion  18 , causing cam follower  22  to raise in a direct relationship to the travel of pin  24  in lift portion  18 . As cam follower  22  is raised, rocker arm assembly  26  is raised, resulting in a raising and closing of valve  30  in valve guide  28 . 
   Conversely, as the rotation of asymmetrical cam groove  16  is continued, pin  24  enters into descent portion  20 , causing cam follower  22  to lower in a direct relationship to the travel of pin  24  in descent portion  20 . As cam follower  22  is lowered, rocker arm assembly  26  is lowered, resulting in a lowering and opening of valve  30  in valve guide  28 . 
   Although only a few exemplary embodiments of the present invention have been described in detail above, those skilled in the art will readily appreciate that numerous modifications to the exemplary embodiments are possible without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the following claims.