|Publication number||US3915129 A|
|Publication date||Oct 28, 1975|
|Filing date||Sep 18, 1974|
|Priority date||Sep 18, 1974|
|Publication number||US 3915129 A, US 3915129A, US-A-3915129, US3915129 A, US3915129A|
|Inventors||Fulghum Leonard Owen, Rust Robert H|
|Original Assignee||Fulghum Leonard Owen, Rust Robert H|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (5), Referenced by (15), Classifications (5)|
|External Links: USPTO, USPTO Assignment, Espacenet|
United States Patent 1191 Rust et a1. 5] Oct. 28, 1975 INTERNAL COMBUSTION ENGINE  Inventors: Robert H. Rust, 1073 Hampton Z"',"f g f 3 Road, Daytona Beach, Fla. 32014; & Leonard Owen Fulghum, 26 63rd Attorney, Agent, or Fzrm-Cus man, ar y St., Savannah, Ga. 31405 Cushman  Filed: Sept. 18, 1974 57 ABSTRACT  Appl. No.: 507,240 In an internal combustion engine of the type having a timing cam with a distance from center to cam surface with varies along its axis of rotation and at least one l23l90.lli%ll4/l5gz cam follower which rides on the cam surface to oper d 0 2 90/16 ate a valve so that the valve operating characteristics o 15 9O vary as a function of the position of the cam follower along the axis of rotation of the cam, the improvement 56 R f Ct d wherein the cam follower includes a ball having a flat 1 e erences l 6 surface engaging the cam surface so that a line of UNITED STATES PATENTS contact always exists between the ball and the cam 1,729,448 9/1929 Michell 74/569 surface and means for mounting said ball in the fol- 2,l5l,832 39 ug i---. 74/569 lower, producing a mechanism which is durable, 3,270,726 9/1966 Cott0n.... 74/569 heap to manufacture and adaptable to present day 3,523,465 8/1970 Harre11.... 123/9018 engines 3,730,150 5/1973 Codner l23/90.l8
1215,7515 2/1924 Michell 74/569 1 Claim, 2 Drawing Figures I zzairt'" US. Patent Oct. 28, 1975 3,915,129
, Z2 Ji 0%? J 1. z Z
INTERNAL COMBUSTION ENGINE BRIEF DESCRIPTION OF THE PRIOR ART AND SUMMARY OF THE INVENTION The invention relates to an improved internal combustion engine of the type having a timing cam and a cam follower which rides on the cam surface to operate a valve.
Heretofore, one of the major compromises affecting the performance of an automobile engine has been valve timing, duration and lift (generally referred to as TDL). Valve TDL determines to a large extend the smoothness and power characteristics of an engine at various RPMs. With conventional engines, due to valve TDL, an engine with a smooth idle is unfortunately limited in its power production at high RPM. Conversely, an engine that produces optimum power at high RPM lacks smoothness and tractability at lower speeds. The reason for this problem is that the breathing characteristics of the engine, i.e., the ability of the engine to draw in a full charge of air-gas mixture into the cylinder and, after combustion, to reject the spent exhaust gasses, changes with engine RPM. In conventional engines, however, the valve TDL is fixed while the breathing characteristics of the engine change with RPM. Accordingly, the valve TDL is conventionally a compromise to produce relatively smooth idle with adequate power at high RPMs. This compromise produces neither optimum smoothness at idle nor optimum power at high RPM. I
One possible technique to deal with this problem which has been suggested in the past is to construct the cam to have a distance from center to cam surface which varies along its axis of rotation. The cam follower can then be shifted along its axis of rotation as a function of engine speed by centrifugal or other mechanisms so that the cam follower rides on a portion of the cam surface which is optimum for the speed at which the engine is rotating. The US. Pat. No. 2,980,089, to Sampietro, is typical of this general type of improved engine.
The primary drawback to improvements of this type in the part is that they provide essentially a single point of contact between the cam follower and the cam surface. The most common mechanism in this type of structure employs a roller having a rounded contour which enables it to follow the varying contours of the cam surface.
However, this single point of contact is insufficient for the surfaces of the cam follower and the cam surface to endure the tremendous pressures which result from the inertia in the valve train mechanism. In contrast with those variable cam arrangements having a point of contact, a conventional lifter has a line of contact of about three-eighths inch with the conventional surface which permits it to stand up under longrange operating conditions.
The present invention relates to an improved internal combustion engine in which a cam follower is employed which includes a ball having a flat surface engaging the cam surface. This engagement results in a line of contact which always exists between the ball and the cam surface. The result is a mechanism which is simple, durable, cheap to manufacture and easily adaptable to present day internal combustion engines.
At least two patents in the prior art describes arrangements of this general type which do not have a single point of contact. The U.S. Pat. No. 3,618,573, to Allen, describes an arrangement in which a universally mounted rocker is used. Such a rocker, however, may not be entirely practical due to the necessity of the rocker mechanism being subjected to tremendous lateral acceleration because the entire rocker must follow the contours of the cam lobe. The US. Pat. No. 3,730,150, to Codner, describes a mechanism in which a roller is used and a line of contact is attempted to be maintained at a fixed angle. This fixed angle is not compatible with varying angles of the cam lobe.
Many other objects and purposes of the invention will be clear from the following detailed description of the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. ll shows a cut-away view of a portion of an improved internal combustion engine of this invention;
FIG. 2 shows a schematic view of the cam follower and can which comprise the improvement of this invention.
DETAILED DESCRIPTION OF THE DRAWINGS Reference is now made to FIGS. 1 and 2 which illustrate the improvement of this invention. As in conventional internal combustion engines, cam 20 is mounted for rotation with the engine and the speed of rotation of the timing cam is a function of the speed of rotation of the engine. Further, cam 20 is mounted in any conventional way so as to be movable along its axis as a function of the engine RPM. Any conventional mechanism, such as the arrangement which is described in the Allen US. Pat. No. 3,618,573, can be employed. Centrifugal, hydraulic, electrical or any other mechanisms for moving the cam shaft can be employed and the way in which that shaft is moved along its axis is not part of the invention of this application.
Also, in the same fashion as in conventional engines, a mechanical cam follower or lifter 22 is mounted for longitudinal movement as it follows the surface of cam 20. It will, of course, be understood that while the embodiment of this application illustrates a mechanical lifter, hydraulic and other conventional lifters can also be employed in the same fashion.
However, in contrast with conventional arrangements, the cam follower 22 in the embodiment of this invention comprises a ball 24 having a flat surface 26 which engages the surface of cam 20. As can be seen in FIG. 2, cam 20 has a distance between its axis of rotation and its surface which varies along the length of that axis so that, as cam 20 is moved in the direction of the arrows of FIG. 2, the flat surface 26 engages different portions thereof to change the TDL characteristics of the valve which is mechanically or otherwise connected to the lifter 22. By using a ball having a flat surface, a continuous line of contact always exists between the ball and the cam surface and this results in a mechanism which is practical, durable, cheap to manufacture and adaptable to present day engines.
Many changes and modifications in the above described embodiment of the invention can, of course, be carried out without departing from the scope thereof. Accordingly, that scope is intended to be limited only by the scope of the appended claims.
What is claimed is:
1. In an internal combustion engine of the type having a timing cam with a distance from center to cam having a flat surface engaging the cam surface so that a line of contact always exists between the ball and the cam surface and means for mounting said ball in said follower.
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|U.S. Classification||123/90.18, 74/569|