OPTIMIZATION OF THE TRIBOLOGICAL AND VIBRATORY BEHAVIOUR OF THE ROCKER ARMS OF A FOUR-VALVE ENGINE

B. FANTINO

bernard.fantino@insa-lyon.fr

B. BOU-SAID

benyebka.bou-said@insa-lyon.fr

Department of Mechanical Engineering, Lithuanian University of Agriculture, LITHUANIA

Abstract. The aim of this work is to model the dynamic and tribological behaviour of the valve train of an industrial vehicle engine and to understand the phenomena involved in its operation. This model allows identifying and quantifying the significant parameters for the optimization of the mechanical system. For instance the results show that the working conditions of such a mechanism give a very important relative axis eccentricity: it can be higher than 0.98 for a radial clearance of 33 µm. This induces very small minimal film thicknesses: lower than 0.33 µm that are of the same order of the surface roughness. The given friction torque becomes zero when the fall speed becomes zero: this allows determining power losses in the contact (P=Cω). The axial flow represents the leak flow due to the hydrodynamic load. This flow is close to the load area and presents some important variations inside the given clearances. It turns out to be very small for the minimum radial clearance, which induces a worse evacuation of the power losses and thus film degradation.
 

Keywords: rocker arm, valve engine, hydrodynamic, power losses

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