Experimental methodology for the tappet characterization of timing system in I.C.E.

The aim of present work is the containment of the inertia forces, the stiffness components optimization and the fit tolerances of valve train in internal combustion engines (I.C.E.) 4T. The proposed methodology allows, through the development of a test machine, the evaluation of axial stiffness of tappet depending on eccentricity of the cam tappet contact, performing a functional analysis that simulate the behaviour of the system in operational condition, even if, some adjustment of tolerances of the fit between tappet and his guide, occurred. The dynamic study of the valve train, through modern computer codes, is performed by connecting lumped masses, springs and dampers that characterize each element. In numerical models the tappet is represented as constituted by the tappet and by the hydraulic element. Each of these elements is characterized by stiffness and mass. The structural rigidity of the tappet has, in fact, important effects on the dynamic behaviour of the entire valve train. The test machine makes possible the choice of the dimensional and geometrical tolerances of the fit between tappet and his guide; allows furthermore the evaluation of errors occurred during construction and integration phase. In addition, the test machine is also suitable for reverse engineering applications, makes it possible to automatically draw the cam profile in polar coordinates.