A Study On Abnormal Abrasion Of Cams For Engines

Valve train is an important part of the engine. Cam and rocker arm withmovement friction subassembly are the key components in the valve train. The authorhas been faced with the abnormal abrasion of their surface, which leaded to reliabilityfailure problems, and analyzed them by Fishbone Diagram one by one. The authorsummed up8aspects about it and found a solution to the problem. Induction,elimination method, experiment and simulation analysis are an important mean andmethods for solving this kind of problems, which has solved many importantengineering questions.The research object is the cam’s abnormal abrasion of the600cc engine,F02/F04type, in this article. The author has recurred the cam’s abnormal abrasion ofF02/F04engine by experiment, which was involved with early scratch. Aimed to8aspect of the abnormal abrasion, the author putted up tests, measurements andanalysis. Then, the author has finally reduced the contact stress between a cam androcker by optimizing the cam profile and improving the initial use in oil lubrication.The following is the main research content and results in this article:(1) About the abnormal abrasion, the author has eliminated relationship withengine working temperature, engine cleanliness, the match materials in the cam androcker, the processing quality of related parts, oil selection, oil pressure, andinstantaneous impact in the starting by tests, measurements and analysis. Then theauthor doubted that friction contact stress in the cam and rocker was too big, so toinvolve the valve train to the abnormal abrasion.(2) Based on the AVL/TYCON software, the F02/F04engine valve mechanismkinematics and dynamics analysis. According to the calculation results, the authorfound the contact stress of the cam and rocker was too big, when the engine speedwas low. It might cause the cam abnormal abrasion and scratch. So the authordesigned the profile of the inlet and exhaust cams, to improve the contact condition ofthe cam and the rocker.(3) By using the cam design module in AVL/TYCON software, the authordesigned the profile of the inlet and exhausts cams and analyzed it by kinematics anddynamics. It has showed that the dynamic performance of valve mechanism improved,the contact stress of the cam rocker reduced, the cam abnormal abrasion avoided. (4) The F02/F04engine performance test has been done, the results showed thatthe engine power and fuel economy have increased slightly. Then measured themodified cam valve acceleration and the radial stress, compared with the calculationresults, they were consistent. It indicated that the simulation method is effective, theoptimization design results are reasonable.