Research On Press-Fitting Process Of Diesel Engine Valve Seat By Test And CAE

As one of the important parts on an engine cylinder head, valve seat combined with valve head is used to seal the cylinder and controls the intake of fresh air and the elimination of exhaust gas, Its performance has influence on fuel consumption, power, efficiency and life of engine. Valve seat working environment is very bad, in addition to withstand the corrosion of high temperature gas, but also to withstand the cylinders explosion pressure and the high-speed impact come from valve. Thus, the press-fitting process is an important process of cylinder head assembly, it makes a directly effect on the quality of the performance, the power output and the life of engine.At first, the paper introduces the research status of valve seat press-fitting in the domestic and overseas, then the structure, the working principles and the press-fitting process is introduced. Secondly, aiming at the practical question jumping over proof of valve seat line and vacuum leakage test, by making contrast test, reasons for the problem were checked, and the improvement measures were proposed.To improve the press-fitting efficiency and reduce the production cost, the new process improvement method that with ATP(Ambient Temperature Press-fitting) instead of freeze pressing were put forward, and a series of test are made to analyze its feasibility. The circumferential strain and F-S(Force-displacement) curves were put forward which can be a criterion for press-fitting reliability.Introduces the theoretical analysis of the interference fit and the theoretical basis of finite element analysis, established the mathematical model, and the formula of combined thick cylinder on the basis of thick cylinder theory was induced to gain the elastic mechanics and its strength check are made.Finally, introduces the solving method of nonlinear contact problem and the correct sitting method of interference in finite element contact; according to theoretical analysis, the stress and strain were acquired by using finite element simulation when the valve seat in the process of installation, and obtained the F-S curves by ANSYS parametric programming.For the subject about the press-fitting of diesel engine valve seat, the practical problem has been solved by the experimental study and improved the press-fitting process, on the basis of theoretical analysis using the finite element method to obtain the results of simulation analysis shown that simulation results are consistent with theoretic results. The feasibility of the finite element simulation analysis was proved, and the reference basis for design of valve seat, process optimization, equipment selection and the choice of interference was provided.