Study On Vibration And Noise From Motorcycle Transmission

At present, China has become the world's largest motorcycle manufacturer, and the problem of noise then comes out. With the Government having promulgated more stringent regulations, the vehicle enterprices have to improve the research of the vibration and noise control to a new level. As a big part of the noise is radiated by the vibration of surface, especially to those parts with thin walls, such as oil pan, air valve cover, transmission cover, motorcycle transmission cover is one of the main components of noise radiation, and according to the theory of acoustics, noise only depends on the main sources. Consequently, the vibration and noise control of motorcycle transmission cover is very significant.Firstly, it is shown in the sound intensity experiment for the type of JS150 motorcycle that the transmission cover is one of the main noise sources and analysised its frequency range of noise, while the surface vibration experiment was carried out at the engine speed of 5100 r/min, 5400 r/min and 7200r/min for getting the vibrational speed of the bolts. The speed can be the load of frequency response analysis.Secondly, the solid model and finite element model was founded, and then got the characteristic parameters such as inherent frequency and vibration mode of the structure by finite element modality analysis. Experiment modal analysis was carried out as well whose result was compared with the results of the theory modal analysis. They coincided pretty well, which proves that the model founded is reliable. On the basis, the boundary element model of gearbox cover was founded. Radiation characteristics of the sound fieldwere, including sound pressure and sound power, were calculated through the acoustic simulation and identified the main frequency bands of noise radiation. The paper found the relational factors which can influence structure noise according to the basic solutions of the radiated noise control and then gave some amendment schemes for this cover.At last, the paper simulated the sound field characteristic of the amendment schemes through the acoustic simulation, and compared the advantages and disadvantages of several improvements for the amendment schemes.