| The valve train is an important part of diesel engine, which influences the economy, emission, NVH and reliability performances directly. Aiming at the YC6108 diesel engine made by the Yuchai Machine Stock Company, the vibration of the valve train and the lubrication film between the cam-tappet pairs have been studied detailedly. This work includes the following aspects: dynamic modeling of valve train; the effect of vibrational behavior with the consideration of manufacturing error of cam profiles; modeling of two-dimentional isothermal transient full film and part film EHL; the application of mulit-grid method in EHL; the lubricating film simulation of the cam-tappet pair with the consideration of dynamic effect.A literature review in vibration and lubricating of valve train has been presented firstly, which was helpful in identifying the key problems.A two-dimentional multi-DOFs nonlinear dynamic model has been established, which is the basis of anlaysing vibration & lubrating film of valve train. Particular attention was focuses on the spring model and the contact between valve and valve seat in order to perfectly describe the dynamic behavior under high-speed conditions. Then, optimization method is adopted to ajust some parameters so as to make the calculation result fit the experiment more exectly. Using this dynamic model, the effects of vibrational behavior with the consideration of manufacturing error of cam profiles have been analysed. The suggestions in valve train design and control of processing technics are presented.A two-dimentional isothermal transient full film and part film EHL model has been established, which is used to analyze lubricational behavior of cam-tappet pair of valve train. Using mulit-gird method, the oil film status during intake duration could be investigated with the consideration of dynamic effect. The influences of surface roughness are also taking into account in the part film model. Based on the fact that during the forming of lubricating film, entraining effect is plays a leading role while squeezing effect only has a minor, suggestions on designment of cam-tappet pair and selection of lubrication oil are presented. |
