Crankshaft for an internal combustion engine

Abstract

A crankshaft for an internal combustion engine comprises at least four main journals aligned on a crankshaft axis of rotation and at least three crankpins, each disposed about a respective crankpin axis and positioned between the main journals. Each of the respective crankpin axes is oriented parallel to, and spaced radially from, the crankshaft axis of rotation. Each of the crankpins is joined to a pair of crank arms for force transmission between the crankpin and the pair of crank arms. Each pair of crank arms is joined to a respective main journal for transmitting torque between the pair of crank arms and the main journal. At least two of the crankpins are positioned substantially in phase with one another and a third crankpin being positioned approximately 180 degrees apart from the at least two crankpins.

What is claimed is: 
     
         1 . A crankshaft for an internal combustion engine comprising:
 at least four main journals aligned on a crankshaft axis of rotation; and   at least three crankpins, each disposed about a respective crankpin axis and positioned between the main journals;   each of the respective crankpin axes being oriented parallel to, and spaced radially from, the crankshaft axis of rotation;   each of the crankpins being joined to a pair of crank arms for force transmission between the crankpin and the pair of crank arms;   each pair of crank arms being joined to a respective main journal for transmitting torque between the pair of crank arms and the main journal;   two of the crankpins being positioned substantially in phase with one another and a third crankpin being positioned approximately 180 degrees apart from the at least two crankpins.   
     
     
         2 . A crankshaft as in  claim 1 , wherein the at least three crankpins form a crankpin grouping in which the outer crankpins are positioned near a first approximate angular location for in-phase rotation about the crankshaft axis of rotation. 
     
     
         3 . A crankshaft as in  claim 2 , wherein the inner crankpin is positioned approximately 180 degrees apart from the first approximate angular location. 
     
     
         4 . A crankshaft as in  claim 1 , wherein the at least three crankpins form a crankpin grouping in which two adjacent crankpins are positioned near a first approximate angular location for in-phase rotation about the crankshaft axis of rotation. 
     
     
         5 . A crankshaft as in  claim 4 , wherein the remaining crankpin is positioned approximately 180 degrees apart from the first approximate angular location. 
     
     
         6 . A crankshaft as in  claim 2 , wherein the crankpin grouping includes four main journals. 
     
     
         7 . A crankshaft as in  claim 6 , wherein each of the crankpins of the crankpin grouping is disposed between a pair of main journals. 
     
     
         8 . A crankshaft as in  claim 2 , wherein the inner crankpin of the crankpin grouping is oriented symmetrically to the outermost two crankpins of the crankpin grouping. 
     
     
         9 . A crankshaft as in  claim 2 , wherein the three crankpins of the crankpin grouping and the axis of rotation of the crankshaft are all disposed approximately in a single plane. 
     
     
         10 . A crankshaft as in  claim 2 , wherein the axes of the outer crankpins of the crankpin grouping are approximately co-linear. 
     
     
         11 . A crankshaft as in  claim 2 , wherein the strokes of the three crankpins of the crankpin grouping are approximately equal. 
     
     
         12 . A crankshaft as in  claim 2 , wherein the strokes of the outer crankpins of the crankpin grouping are greater than the stroke of the inner crankpin. 
     
     
         13 . A crankshaft as in  claim 2 , wherein the strokes of the outer crankpins of the crankpin grouping are less than the stroke of the inner crankpin. 
     
     
         14 . A rotating group for a three cylinder internal combustion engine, the rotating group comprising:
 three pistons, each associated with a respective cylinder and connected through a respective connecting rod to a respective crankpin, the crankpins being disposed on a single crankshaft;   wherein the crankshaft comprises:
 at least four main journals aligned on a crankshaft axis of rotation; and 
 at least three crankpins, each disposed about a respective crankpin axis and positioned between the main journals; 
 each of the respective crankpin axes being oriented parallel to, and spaced radially from, the crankshaft axis of rotation; 
 each of the crankpins being joined to a pair of crank arms for force transmission between the crankpin and the pair of crank arms; 
 each pair of crank arms being joined to a respective main journal for transmitting torque between the pair of crank arms and the main journal; and 
 at least two of the crankpins being positioned substantially in phase with one another and a third crankpin being positioned approximately 180 degrees apart from the at least two crankpins. 
   
     
     
         15 . A rotating group as in  claim 14 , wherein the at least three crankpins form a crankpin grouping in which the outer crankpins are positioned near a first approximate angular location for in-phase rotation about the crankshaft axis of rotation. 
     
     
         16 . A rotating group as in  claim 15 , wherein the inner crankpin is positioned approximately 180 degrees apart from the first approximate angular location. 
     
     
         17 . A rotating group as in  claim 15 , wherein each of the crankpins of the crankpin grouping is disposed between a pair of main journals. 
     
     
         18 . A crankshaft as in  claim 15 , wherein the three crankpins of the crankpin grouping and the axis of rotation of the crankshaft are all disposed approximately in a single plane. 
     
     
         19 . A crankshaft as in  claim 15 , wherein the strokes of the outer crankpins of the crankpin grouping are greater than the stroke of the inner crankpin. 
     
     
         20 . A crankshaft as in  claim 15 , wherein the strokes of the outer crankpins of the crankpin grouping are less than the stroke of the inner crankpin.