Valve train for internal combustion engine

Abstract

A system for varying valve timing; i.e. the rotational angle of the crankshaft during which an intake or an exhaust valve of a cylinder of a reciprocating internal combustion engine is open which results in varying valve overlap, and for varying valve lift of such intake and exhaust valves. A desmodromic cam and cam follower convert rotation of a cam shaft to reciprocating rotation, or oscillation, of the cam follower. The reciprocating rotation of the cam follower is converted by the interaction of a secondary cylindrical cam, a cylindrical control ring, and a reciprocating member to linear motion of the reciprocating member which reciprocating member is operatively connected to a poppet valve. Timing and lift of the reciprocating member and valve are variable over predetermined limits as a function of engine rpm and load by rotation of the cylindrical control ring. Each valve train positively closes as well as opens its associated valve.

What is claimed is: 
     
       1. A valve train for a poppet valve of a reciprocating internal combustion engine comprising: an internal combustion engine;   a cam shaft having an axis of rotation and being mounted on said engine for rotation about its axis at angular velocities which are a function of engine rpm;   means forming a cam surface on said shaft;   a cam follower having an axis of rotation;   means for mounting said cam follower on said engine in engagement with the cam surface of said cam shaft to convert rotation of said cam shaft into reciprocating rotation of said cam follower about its axis of rotation;   a reciprocating member having projecting means;   cam means operatively connected to said cam follower;   movable control means concentrically mounted with respect to said cam means;   said cam means, control means and projecting means interacting to convert reciprocal rotation of said cam follower to reciprocating linear motion of the reciprocating member substantially along the axis of rotation of said cam follower;   said cam means and control means varying the amplification and timing of said reciprocating member with respect to the angular position of the cam shaft as a function of the position of said control means with respect to said engine;   servo means operatively connected to the control means to vary the control means position to vary the amplitude and timing of the reciprocating member as a function of engine rpm and load;   a poppet valve; and   means for operatively connecting said valve to said reciprocating member.   
     
     
       2. The valve train of claim 1 in which the means for operatively connecting said valve to said reciprocating member include a rocker arm pivotally mounted on said engine. 
     
     
       3. In a reciprocating internal combustion engine having a cam shaft mounted on the engine for rotation around the cam shaft's longitudinal axis as a function of engine rpm, the improvements comprising: means forming a circular cam surface on said cam shaft;   a cam follower having an axis of rotation;   means for mounting the cam follower on the engine to engage the circular cam surface of the cam shaft to convert rotation of the cam shaft into oscillations of said first cam follower through substantially an angle alpha about the cam follower's axis of rotation for each complete rotation of the cam shaft;   first and second hollow cylindrical members, each member having a longitudinal axis, the members being dimensioned so that one slidably fits within the others so when they are so positioned their longitudinal axes substantially coincide;   means forming a pair of cam slots in the first cylindrical member, each slot extending substantially over an angle beta with respect to the first member's axis of rotation, a portion of each slot at corresponding portions extending over an angle gamma with respect to the first member's axis of rotation being substantially horizontal;   means adapted to operationally connect said first member to the cam follower so that the longitudinal axis of the first member substantially coincides with the axis of rotation of the cam follower;   means forming a pair of guide slots in the second member, the slots being substantially parallel to the longitudinal axis of the second member;   resilient means for maintaining said second member concentric with the first member, for slidably engaging the first member and for positioning the first member in operational connection with the cam follower so that the first member oscillates with the cam follower;   a reciprocating member mounted within said first and second members, the reciprocating member having means for engaging the cam and guide slots of said first and second members; and   means for positioning the second member relative to the engine as a function of engine rpm and load to vary the timing and magnitude of movement of the reciprocating member with respect to the same shaft;   a poppet valve; and   means for operatively connecting the valve to the reciprocating member.   
     
     
       4. In the engine of claim 3 in which the means for operatively connecting the valve to the reciprocating member include a rocker arm pivotally mounted on the engine. 
     
     
       5. In the engine of claim 3 in which the angle alpha is 90°, the angle beta is 120°, and the angle gamma is 30°. 
     
     
       6. A valve operating mechanism for a reciprocating internal combustion engine, which mechanism converts rotational motion of a cam shaft which rotates around its longitudinal axis as a function of engine rpm into reciprocating linear motion of a reciprocating member operatively connected to a valve, and varies the timing and magnitude of movement of the valve as a function of engine rpm and load, comprising: means forming a circular cam surface on said cam shaft;   a cam follower having an axis of rotation;   a pin having a longitudinal axis, the pin being mounted on the cam follower so that its longitudinal axis is substantially parallel to the axis of rotation of the cam follower but offset from it;   a bushing mounted on the pin;   means for mounting the cam follower with respect to the cam shaft so that the bushing engages the circular cam surface to convert rotation of the cam shaft into reciprocal rotation of the cam follower about its axis of rotation;   a first hollow cylindrical member having a longitudinal axis;   means forming a pair of cam slots in the first member;   means adapted to operationally connect the first member to the cam follower to cause the first member to oscillate about its longitudinal axis with the cam follower;   a second hollow cylindrical member having a longitudinal axis;   means forming a pair of guide slots in the second member, said slots being substantially parallel to the second member's longitudinal axis;   resilient means for mounting the second member so that it is substantially concentric with the first cylindrical member and so that the first member is operatively connected to the cam follower;   a reciprocating member;   projecting means formed on the reciprocating member;   the reciprocating member being positioned within the first and second members with its projecting means engaging the cam slots and guide slots of the first and second members;   means for rotating the second member about its axis relative to the means for mounting the cam follower as a function of the speed and load mechanism of the engine;   a poppet valve; and   means for operatively connecting the valve to the reciprocating member.   
     
     
       7. The valve operating mechanism of claim 6 in which the resilient means is a coil spring. 
     
     
       8. The valve operating mechanism of claim 6 in which the means for operatively connecting the valve to the reciprocating member include a rocker arm pivotally mounted on the engine. 
     
     
       9. In a reciprocating internal combustion engine having a crankshaft, a valve train comprising: a cam shaft having an axis of rotation;   bearing means on the engine mounting the cam shaft for rotation around its axis;   means connecting the cam shaft to the crankshaft of the engine so that the angular velocity of the cam shaft is one-half that of the crankshaft;   a cam surface of circular cross section formed on the cam shaft;   a cam follower having a cylindrical portion, the cylindrical portion having an axis of rotation;   a pin having a longitudinal axis, the pin being mounted on one end of the cylindrical portion so that the pin's longitudinal axis is substantially parallel to the cylindrical portion's axis of rotation but displaced a fixed distance;   a cam follower bushing mounted on the pin;   a cylindrical disk attached to the other end of the cylindrical portion of the cylindrical portion of the cam follower;   means forming a plurality of notches around the periphery of the cylindrical disk of the cam follower;   a journal bearing in the engine, the cylindrical portion of the cam follower mounted in the journal bearing for rotation about its axis of rotation and with the cam follower bushing contacting the cam surface of the cam shaft, the path of the cam surface being such that rotation of the cam shaft causes the cam follower to oscillate through a predetermined angle about its axis of rotation;   a secondary cam having cylindrical walls and longitudinal axis;   means forming a pair of cam slots in the walls of the secondary cam;   a plurality of lugs formed on the secondary cam;   a control ring having cylindrical walls and a longitudinal axis;   a cylindrical disk attached near the bottom of the control ring;   means forming a pair of guide slots in the cylindrical walls of the control ring, said slots being substantially parallel to its longitudinal axis;   the diameter of the outer cylindrical wall of the control ring being slightly less than the diameter of the inner cylindrical wall of the secondary cam;   the secondary cam being mounted around the exterior of the cylindrical walls of the control ring, the lugs on the secondary cam adapted to fit into the means forming notches of the cam follower;   a coil spring positioned between the engine and the bottom surface of the cylindrical disk of the control ring or maintaining the lugs of the secondary cam in the means forming notches in the cylindrical disk of the cam follower so that they will oscillate together;   a valve keeper positioned for linear movement within the inner cylindrical wall of the control ring;   means forming a transverse bore through the keeper;   means forming a vertical bore through the keeper;   a cross pin located in the transverse bore and engaging the means forming cam slots in the secondary cam and the means forming guide slots in the control ring;   a poppet valve;   key means for fixedly securing the valve to the valve keeper;   a drive pin mounted on the cylindrical disk of the control ring; and   a servo mechanism connected to the drive pin, the servo mechanism also being connected to the engine and responsive to engine rpm and load for varying the angular position of the control ring with respect to the engine as a function of engine rpm and load, whereby the timing and lift of the valve varies as a function of engine rpm and .[.speed.]. .Iadd.load.Iaddend.. .Iadd. 10. A valve train for a poppet valve of a reciprocating piston engine comprising:   a piston engine;   a cam shaft having an axis of rotation and being mounted on said engine for rotation about its axis at angular velocities which are a function of engine rpm;   means forming a cam surface on said shaft;   a cam follower having an axis of rotation;   means for mounting said cam follower on said engine in engagement with the cam surface of said cam shaft to convert rotation of said cam shaft into reciprocating rotation of said cam follower about its axis of rotation;   a reciprocating member having projecting means;   cam means operatively connected to said cam follower;   movable control means concentrically mounted with respect to said cam means;   said cam means, control means and projecting means interacting to convert reciprocal rotation of said cam follower to reciprocating linear motion of the reciprocating member substantially along the axis of rotation of said cam follower;   said cam means and control means varying the timing of said reciprocating member with respect to the angular position of the cam shaft as a function of the position of said control means with respect to said engine;   means operatively connected to the control means to vary the control means position to vary the timing of the reciprocating member;   a poppet valve; and   means for operatively connecting said valve to said reciprocating member.   
     
     
        .Iaddend. .Iadd. 11.  A valve train for a poppet valve of a reciprocating piston engine comprising: an internal combustion engine;   a cam shaft having an axis of rotation and being mounted on said engine for rotation about its axis at angular velocities which are a function of engine rpm;   means forming a cam surface on said shaft;   a cam follower having an axis of rotation;   means for mounting said cam follower on said engine in engagement with the cam surface of said cam shaft to convert rotation of said cam shaft into reciprocating rotation of said cam follower about its axis of rotation;   a reciprocating member having projecting means;   cam means operatively connected to said cam follower;   movable control means concentrically mounted with respect to said cam means;   said cam means, control means and projecting means interacting to convert reciprocal rotation of said cam follower to reciprocating linear motion of the reciprocating member substantially along the axis of rotation of said cam follower;   said cam means and control means varying the timing of said reciprocating member with respect to the angular position of the cam shaft as a function of the position of said control means with respect to said engine;   servo means operatively connected to the control means to vary the control means position to vary the timing of the reciprocating member as a function of engine rpm;   a poppet valve; and   means for operatively connecting said valve to said reciprocating member. .Iaddend.