Engine tubular camshaft assembly with multi-lift cam sets and method

Abstract

An engine camshaft assembly includes a hollow tubular shaft mounting a plurality of separate cam sets, each including multiple camps. Each cam includes an outer cam surface bounded by opposite parallel sides and including an axial opening extending through said sides. Each cam set includes at least two associated cams positioned in side-by-side relation with their openings axially aligned. A shoulder protruding from a side of one of the cam engages an adjacent side of another associated cam, thus maintaining the sides of the associated cams in fixed parallel relation. The tubular shaft extends through the cam openings and supports the cam sets on a common rotational axis. During assembly, the shaft is expanded into engagement with the openings so that the cam sets are retained in fixed axial and angular relation on the shaft.

1 . An engine camshaft assembly rotatable on a rotational axis and comprising:
 a hollow tubular shaft and a plurality of separate cam sets each including multiple cams;   each cam including an outer cam surface bounded by opposite parallel sides and an axial opening extending through the sides;   each cam set including at least two associated cams positioned in side by side relation with their openings axially aligned and a shoulder protruding from a side of one of the cams and engaging an adjacent side of an other associated cam, thus maintaining the sides of the associated cams in fixed parallel relation;   the tubular shaft extending through the cam openings and supporting the cam sets on a common axis, the shaft being expanded into engagement with the openings so that the cam sets are retained in fixed axial and angular relation on the shaft.   
     
     
         2 . An assembly as in  claim 1 , wherein the outer cam surfaces are finished by grinding after assembly of the cam sets to the shaft. 
     
     
         3 . An assembly as in  claim 1 , including camshaft bearing journals formed between at least selected pairs of cam sets and having bearing surfaces formed by grinding after assembly of the camshaft. 
     
     
         4 . An assembly as in  claim 3 , wherein the bearing journals are formed on steel bearing sleeves fixed by expansion of the tubular shaft within the sleeves. 
     
     
         5 . An assembly as in  claim 4 , wherein the bearing sleeves include ground parallel ends engaging the sides of adjacent cams in the cam sets and assisting in maintaining the parallel relation of the cams in the cam sets of the camshaft assembly. 
     
     
         6 . An assembly as in  claim 1 , wherein at least some of the cam sets include cams having differing eccentricities for actuation of two-step valve lifters. 
     
     
         7 . An assembly as in  claim 1 , including cam sets for actuation of two-step valve lifters, each such cam set including a low lift central cam positioned between two high lifter end cams. 
     
     
         8 . An assembly as in  claim 7 , wherein the central cams are formed of hardened steel for actuation of roller followers and the end cams are formed of cast iron for actuation of sliding cam followers. 
     
     
         9 . An assembly as in  claim 8 , wherein the central cams have shoulders extending from both sides and engaging the sides of the associated end cams to provide a predetermined spacing of the outer cam surfaces from one another.