Optimized Improvement Design Of The Engine Valve Train

Valve Train is an important component of the engine. The rationality of its design is directly related to the engine's power performance, fuel economy, emission performance, reliability and durability. Along with high speed and power of the engine, people were getting higher and higher to its performance index. The Request is under the high speed movement condition, the valve train still be able to steady and work reliably, thus set a higher request to the valve train. Cam profile is the hard core of the valve train. So the cam profile design is one of the most important approach of the valve train optimum design. The analog computation of the cam profile match with the engine performance is an important research method of valve train.This article has been based in the full research of the related domestic and foreign literatures. Systematically summarized the present situation of valve train. And then the detailed research of cam profile evaluating indicator as well as kinematic and dynamic analysis of the valve train have been done. The widely used valve-train simulation software, AVL-TYCON, was applied to perform both kinematic and dynamic simulations for the valve train of a four-cylinder gasoline engine of the project. Simulation results indicated that the original valve train has some design drawbacks which may lead to durability issues. Then combine manufacturer's requirements of the engine performance, The intake and exhaust cams profile were redesigned, via computer simulation optimization with GT-POWER software, which not only solved the primary design issues and improved the durability, engine performance simulation results also indicated an improvement to the full load volumetric efficiency, which resulted in an increase of maximum engine power output and torque capacity. And this fulfilled manufacturer's requests. At present, the new cam profile is in a manufacturing process. We will be confirming this research conclusion accuracy afterward through the engine bench test. The main research of the article include the following works:(1)Applied the valve simulation software AVL-TYCON to do the valve train kinematic and dynamic calculation of the gasoline engine. Calculations and analysis results showed that the intake and exhaust valve of original engine can't open and close quickly. Plump coefficient and time area of the intake and exhaust valve are low, this will go against improve the volumetric efficiency of the engine. The greatest jerk valve of the intake and exhaust is more than the normal range, this will makes the valve train oscillation more serious. The contact stresses between cam and tappet is greater, this will makes abrasion between cam and tappet serious. Lubrication coefficient between cam and tappet is lower, so lubrication condition of liquid dynamics between cam and tappet is unsatisfactory. In response to these questions, the improvement design measure and method of the cam profile has been brought up.(2)The main influencing factors of Cam profile design are discussed, and optimized design plan has been brought up. Through redesign of the intake and exhaust cam profile, the kinematic and dynamic characteristics have improved. This not only solved the problems of the original engine, but also improved the reliability and life of the valve train.(3)Applying the GT-POWER software to do the performance simulation of the engine. Performance simulation results indicated an improvement to the full load volumetric efficiency, which resulted in an increase of maximum engine power output and torque capacity. So fulfilled manufacturer's requests.