Investigation on cam-follower lubricated contacts

The cam-follower contact is one of the most complex lubricated non-conformal contact due to its continuous variation of load, speed and geometry. The complexity of the phenomena occurring in the camshaft systems make experimental verifications very important. In this work, an already existing versatile experimental apparatus for investigation of non-conformal lubricated contacts, able to measure film thickness using the optical interference method and friction force trough a load cell, has been modified in order to tests cam-follower contacts. Some test have been carried out for investigating the behaviour of some fundamental components of the rig. A theoretical/numerical simulations has been performed to investigate the dynamic behaviour of the system and in order to provide some indications for the interpretation of the experimental results. Purposely developed versions of the programme have been also an important support for the design and of a new apparatus specifically addressed to the cam-follower contact and with increased potentialities capable of more detailed measurement of film thickness and contact forces. The apparatus is able to reproduce a cam-follower mechanism that uses a rocker as a link device between the cam follower set and the valve

Wear and elastohydrodynamic lubrication studies of cams and followers

The concentrated non-conformal contact between the cam and the follower is one of the most severe working tribological components in the internal combustion engine. Due to the continuous variation of load, speed and geometry, this contact is very difficult to be investigated. This work is mainly devoted to review the wear and elastohydrodynamic film thickness studies related to this important engine mechanism and is divided into two parts. In the first part a review is made of theoretical/numerical studies addressed to predict the film thickness, pressure distribution and their relations with the most common surface failures as pitting and scuffing. The second part is committed to show the experimental efforts that have been carried out to estimate the real film thickness and the force friction in order to improve the durability of mating cam/follower surfaces under elastohydrodynamic lubricating regimen. A new versatile experimental apparatus under development is also presented

Experimental study of engine cam-followers

The cam-follower pair is a very complex lubricated contact because its continuous variation of load, speed and radius of curvature. Experimental verification are necessary but very difficult to perform. After a literature review of the existing test rigs for cam-follower simulation, the main aspects of a new versatile apparatus are presented. Several design variations are presented, each one with its advantages and drawbacks. The final project will take into account some of the presented design solutions and the results of dynamic simulations of the rigs currently under elaboration