Design And Research On Valve Train In Automobile Engine

Valve train is the core components, its design is reasonable for the internal combustion engine power, economy, environmental protection and the reliability of the work. Based on the study of present status and development trend of valve train home and abroad, the structural type suitable for work environment and performance requirement of Q276 Engine was adopted with the guide of basic theory of mechanical design, and cam profile, valve timing and power loss were also analyzed, for which were the key influence factors of engine performance. What's more, how to further enhance the type of engine power and economy were discussed.Overhead valve train with a simple body and precise characteristics of gas phase meets the needs of Q276 engine well both on work environment and performance, so overhead valve train was used for Q276 engine. An analysis on the relationship between the speed ad power, speed and torque was made, and then the rated speed of the engine was determined, which laid a foundation for the follow work.The valve train is driven by the cam, so valve train performance depends largely on the shape of cam valve train. Based on in-depth study the internal combustion engine valve train-cam design on the basis of theory proposed and constructed a new line-cam valve train. With the guide of basic theory on the internal combustion engine valve train-cam design, a new cam profile was proposed and constructed. It is smooth and continuous and can increase the fullness, reduce the engine noise. According to the Q276 engine speed, a valve timing matched with it was determined after the impact analysis of advance angle, delay shut angle and valve overlap angle on the volumetric efficiency.A phenomenon that the power consumption caused by the camshaft resistance moment accounted for 9.4 percent of the rated power was found, during the design process of the engine valve train. There were two ways proposed to enhance the effective power of the engine through analysis on the camshaft force model. One was reducing the friction force by rolling friction instead of sliding friction, and the other one was reducing the resistance arm by changing the rack structure.Dynamic, economic and environmental indicators of Q276 Engine were received from performance tests and external characteristic was obtained by bench test. Tests showed that engine has achieved the targets of the design requirements. Research which was about the application on engine and the current level of the Variable Valve timing showed that this technology was widely used on hi-class automotive and application situation was variable manufactured by different manufacturers.Based on the research, two tentative designs were proposed, through which variable valve timing was applied on the small engine. They were variable valve phase and variable intake and exhaust systems. The proposals offered certain value for reference for the engine upgrade of this kind.