The Analysis of a Distribution Mechanism for the Miller-Atkinson Cycle

摘要

In this paper the authors consider a classic distribution mechanism designed to implement the Miller-Atkinson cycle for an internal combustion engine. The mechanism was presented in a previous paper and it is characterized by the spherical head of valve and the asymmetrical motion of the roller of the lever on the spherical head. Only the contact between the roller of the lever and the valve is considered here, the synthesis of the cam being the object of another study. In our paper we extend the discussion for the vibration of the lever considering its angular velocity and acceleration with respect to the rotational angle of the shaft. The analysis of the non-linear vibration of the lever is performed with respect to different geometric parameters: radius of the spherical head of the valve, radius of the roller of the lever, dimensions and positions of different elements. The maximum values of the angular velocity and acceleration of the lever are highlighted in each case by numerical simulation. A great attention is paid to the relative motion between the roller and the spherical head of the valve, which is a measure of the wear of these two elements. The same problem of wear is discussed for the vibrations of the lever in its joint with the aid of the angular velocity and acceleration. The authors also discuss the particular case of the flat head of the valve. In this paper we consider different laws of displacement of the valve in function of the angle of rotation of the shaft; for each such a law we perform a complete discussion using the results obtained by numerical methods. The most important characteristic of these laws of motion of the valve is that they simulate the Miller-Atkinson cycle of the internal combustion engine. The analysis is performed from the kinematic point of view, the authors highlighting the advantages and disadvantages of the laws of motion considered in their study.