Groove-Less Piston and Tapered Press Fit Hydraulic Lash Adjuster

Abstract

A pushrod assembly for an engine is disclosed. The pushrod assembly may include a first piece configured to house a hydraulic lash adjuster and a second piece coupled to the first piece. The first piece may include a mating portion with a tapered end section. The second piece may include a first bore adapted to receive the mating portion of the first piece.

What is claimed is: 
     
         1 . A pushrod assembly for an engine, comprising:
 a first piece configured to house a hydraulic lash adjuster, the first piece including a mating portion with a tapered end section; and   a second piece coupled to the first piece, the second piece including a first bore adapted to receive the mating portion of the first piece.   
     
     
         2 . The pushrod assembly of  claim 1 , wherein the mating portion includes a middle section having a mating surface in press fit engagement with a mating section of the first bore. 
     
     
         3 . The pushrod assembly of  claim 2 , wherein the tapered end section decreases in cross-sectional area from the middle section to an end of the first piece. 
     
     
         4 . The pushrod assembly of  claim 3 , wherein a diameter of the tapered end section is less than a diameter of the mating section of the first bore. 
     
     
         5 . The pushrod assembly of  claim 4 , wherein the end of the first piece includes a chamfered edge. 
     
     
         6 . The pushrod assembly of  claim 5 , wherein the first bore includes a curved end surface. 
     
     
         7 . The pushrod assembly of  claim 6 , wherein the curved end surface of the first bore is generally hemispherical in shape. 
     
     
         8 . The pushrod assembly of  claim 7 , wherein the first bore further includes a gap between the curved end surface and the end of the first piece. 
     
     
         9 . The pushrod assembly of  claim 8 , wherein the first bore gradually decreases in diameter from the mating section to the curved end surface. 
     
     
         10 . The pushrod assembly of  claim 9 , further comprising a third piece coupled to the second piece, the third piece including a mating portion with a tapered end section. 
     
     
         11 . The pushrod assembly of  claim 10 , wherein the second piece includes a second bore adapted to receive the mating portion of the third piece, the second bore including a curved end surface. 
     
     
         12 . The pushrod assembly of  claim 11 , wherein the hydraulic lash adjuster includes a groove-less piston to prevent recirculation of hydraulic fluid. 
     
     
         13 . A valve train for an engine, the valve train comprising:
 a camshaft;   a lifter in contact with the camshaft; and   a pushrod assembly mounted on the lifter and operatively configured to translate motion from the camshaft to a rocker for actuation of a valve, the pushrod assembly including:
 a hydraulic lash adjuster operatively connected to the rocker, 
 a first piece configured to house the hydraulic lash adjuster, the first piece including a mating portion with a tapered end section, 
 a second piece coupled to the first piece, the second piece extending from a first end to a second end, the first end including a first bore adapted to receive the mating portion of the first piece, the first bore including a curved end surface. 
   
     
     
         14 . The valve train of  claim 13 , wherein the hydraulic lash adjuster includes a piston, an exterior of the piston having no grooves for hydraulic fluid recirculation. 
     
     
         15 . The valve train of  claim 14 , wherein the exterior of the piston is smooth and continuous from a first end of the piston to a second end of the piston. 
     
     
         16 . The valve train of  claim 15 , wherein the pushrod assembly further includes a third piece coupled to the second piece, the third piece including a mating portion with a tapered end section, the second end of the second piece including a second bore adapted to receive the mating portion of the third piece, the second bore including a curved end surface. 
     
     
         17 . The valve train of  claim 16 , wherein each of the mating portions of the first piece and the third piece includes a middle section having a mating surface in press fit engagement with a mating section of each of the first bore and the second bore, respectively. 
     
     
         18 . The valve train of  claim 17 , wherein each of the tapered end sections of the first piece and the third piece decreases in cross-sectional area to an end of each of the first piece and the third piece, respectively. 
     
     
         19 . The valve train of  claim 18 , wherein a diameter of each of the tapered end sections of the first piece and the third piece is less than a diameter of the mating section of each of the first bore and the second bore, respectively. 
     
     
         20 . A method for constructing a pushrod assembly, the method comprising:
 leading a tapered end section of a first piece of the pushrod assembly into a first bore of a second piece of the pushrod assembly, the first piece including a hydraulic lash adjuster, a diameter of the tapered end section being less than a diameter of the first bore; and   coupling the first piece to the second piece via a press fit engagement between a mating portion of the first piece and the first bore of the second piece.