Vibration Analysis & Improved Design Of Micro Car Drive Shaft

The vehicle powertrain is a multi-freedom torsional vibration system, and its NVH directly affects easiness and safety of the whole vehicle. One of the main sources of vibration is from the drive shaft. It is necessary to research the NVH of drive shaft and to carry out rational layout and design to the drive shaft which is the fundamental ways of all.In this paper,some research methods of the domestic and foreign have been applied to analyze the vibration of drive shaft of one micro car which has better economy. Furthermore, the vibration problem due to the vibration of drive shaft has been resolved by optimizing the drive shaft layout.Based on simulation analysis,this paper also studies the kinematic characteristics of drive shaft.This paper mainly analyzes the kinematics and dynamics of the drive shaft based on theory, the vibration acceleration test,the vibration frequency test,the experimental modality analysis, and finally found the primary causes to the vibration of the vehicle powertrain.1) The installation angle is too large.2) The first order flexural resonance caused by the rotation frequency of the engine powertrain.3)The center support and suspension vibration isolation function is not good. In view of the question causes,this article proposed the concrete improvement program.1) Through vehicle testing:engine idling,3rd gear with and without drive shaft,3rd gear with and without wheel, found out the drive shaft is the main source of motivation. Use three variable dynamic optimization method to optimize the layout of drive shaft to control the installation angle size.2) Use experimental modality analysis to obtain each modal parameter, compared to the result of vibration frequency test, found that the first bending mode frequency of vehicle powertrain is consistent with the engine excitation frequency. Therefore, to determine that the vibration severe problem is due to powertrain resonance. Through optimization design of the stiffness of center support to coordinate the natural frequency of transmission, so as to make the resonance speed below the common speed of the vehicle; 3) According to the vibration isolation theory, this paper adopts the drive shaft center support which is dynamic stiffness, this enables the center support to have bigger damping at low frequency, or else lower stiffness at high frequency, so the vibration isolation effect is more evident.At the same time this paper reduces the stiffness of suspension to make it with better vibration damping effect.This paper also applies software to simulate the vibration characteristics of drive shaft,in order to emphasize the importance to control the installation angle.The verification result indicates that the solution of drive shaft vibration is effective.It reduced the vibration obviously, and provided a practical approach to solve the vibration of the vehicle caused by drive shaft.