Characterisation of wear on a cam follower system in a diesel engine

Abstract

This paper presents an investigation of the running in of the most important contact surfaces of a modern diesel cam follower system. The test equipment used consists of a commercially available cylinder head with an overhead camshaft and valve train system for six cylinders. The load on the contacting surfaces is varied by controlling the fuel injector pumps. The running in is investigated by analysing the changes in topography of the roller, pin and rocker arm of the fuel injector arm. Seven test series were conducted for 1, 10 and 100 h with a variation of the load and speed between a high and low level. The test time was not long enough to be able to see any changes in the surface topography of the roller or pin surfaces. However the wear on the roller bearing surface and the rocker arm bearing surface was significant. Here the surface peak heights are worn off and the surfaces are smoothed out. The observed changes in surface topography are related to the current lubrication regime and the wear is discussed in terms of the λ-value.