Rotationally Balanced Camshaft Assembly

Abstract

A method for intentionally imbalancing one or more mass elements of a camshaft assembly to provide overall rotational balance to the assembly, also referred to herein as “zero balance”. Such intentional imbalance may be imparted to any element of a camshaft assembly. In a currently-preferred embodiment, one or more components of an improved camshaft phaser assembly are manufactured as rotationally unbalanced, either by intentionally forming an unbalanced component such as a sprocket wheel having added material or by removing non-functional material from an otherwise standard component. Because the camshaft phaser assembly has a unique and fixed angular relationship to the camshaft, zero balance can be readily and repeatedly achieved for all camshaft assemblies by correct manufacture of parts without requiring separate balancing for each individual camshaft assembly as manufactured.

1 . A method for forming a rotationally balanced camshaft assembly for an internal combustion engine, the camshaft assembly including at least a camshaft having at least one eccentric cam, and a camshaft phaser, the method comprising the steps of:
 a) determining the magnitude of rotational imbalance of an unbalanced camshaft assembly; and   b) adjusting the magnitude of rotational imbalance of at least one component of said unbalanced camshaft assembly to compensate for said magnitude of rotational imbalance of said unbalanced camshaft assembly to yield said rotationally balanced camshaft assembly.   
     
     
         2 . A method in accordance with  claim 1  wherein said at least one component is an element of said camshaft phaser. 
     
     
         3 . A method in accordance with  claim 2  wherein said element is selected from the group consisting of sprocket wheel, stator, rotor, cover plate, and target wheel. 
     
     
         4 . A method in accordance with  claim 1  wherein said adjusting step includes the step of forming said at least one component in a predetermined unbalanced arrangement. 
     
     
         5 . A method in accordance with  claim 4  wherein said forming step includes addition of material to said at least one component to cause said predetermined unbalanced arrangement. 
     
     
         6 . A method in accordance with  claim 4  wherein said forming step includes subtraction of material from said at least one component to cause said predetermined unbalanced arrangement. 
     
     
         7 . A method in accordance with  claim 1  wherein said component is a counterweight added eccentrically to said camshaft assembly expressly to rotationally balance said camshaft assembly. 
     
     
         8 . A camshaft assembly comprising a plurality of components wherein at least one of said components is intentionally rotationally unbalanced such that said camshaft assembly is rotationally balanced. 
     
     
         9 . A camshaft assembly in accordance with  claim 8  comprising at least a camshaft having at least one eccentric cam, and a camshaft phaser, wherein said at least one component is an element of said camshaft phaser. 
     
     
         10 . A camshaft assembly in accordance with  claim 9  wherein said element is selected from the group consisting of sprocket wheel, stator, cover plate, and target wheel. 
     
     
         11 . A camshaft assembly in accordance with  claim 9  wherein said at least one component is formed in a predetermined unbalanced arrangement. 
     
     
         12 . A camshaft assembly in accordance with  claim 11  wherein said predetermined unbalanced arrangement includes addition of material to said at least one component. 
     
     
         13 . A camshaft assembly in accordance with  claim 11  wherein said predetermined unbalanced arrangement includes removal of material from said at least one component. 
     
     
         14 . A camshaft assembly in accordance with  claim 8  wherein said at least one component is a counterweight added eccentrically to said camshaft assembly expressly to rotationally balance said camshaft assembly. 
     
     
         15 . An internal combustion engine having at least one camshaft assembly wherein at least one component of said camshaft assembly is intentionally rotationally unbalanced in a predetermined unbalanced arrangement such that the overall camshaft assembly is rotationally balanced.