Analyze Rattle Noise In Automobile Transmissions And Study On The Control Methods

Rattle noise in automotive transmissions is from gear rattle vibration, which is oneof the main sources of automotive transmission noise, and it is one of automobile noisewhich users complain about most and automobile companies pay much attention to. Therattle noise is one kind of transient noise and the noise level will produce a significantjump phenomenon. The human ear may be more sensitive to the changeable magnitude.Therefore, it is necessary to study rattle vibration, rattle noise and the control methods.The paper analyzes the mechanism of rattle noise, sets up the rattling mathematicalmodels of gear systems and an automotive transmission, researches the characteristicsof rattle vibration and noise combined with experiments, and takes some measures tolower the rattle vibration and noise. Hence, the subject has important theoreticalsignificance and engineering significance on building the rattle model of automotivetransmissions and the control methods of rattle vibration and noise.Firstly, the transmission rattle noise mechanism is studies by discussing the gearrattle mechanism, transmission rattle noise mechanism, and the transmission systemdynamic characteristics. The result shows that the internal excitation, external excitationand gear backlash are the main reason of the gear rattle, the driving torque in drivengear determines whether the gear rattle appears, and the rattle intensity as well as thetransmission system dynamic characteristics determines the rattle noise level ofautomotive transmissions.Secondly, gear rattle models with one freedom and five freedoms are set up, inwhich the time-varying meshing stiffness, transmission errors, gear backlash andexternal excitation are considered. The characteristics of rattle vibration are studies bynumerical simulation. Because the theoretical models can not entirely replace the actualgear system, a rattle vibration and noise test rig is designed and built. The simulationresults show that the internal and external excitation, gear mesh stiffness, gear meshingdamping, and gear shaft torsional stiffness have a great impact on the rattle state,periodic response characteristics and rattle intensity. The results of experiment showthat the RMS driven gear angular acceleration of experiment and simulation change bythe same trend, the noise produced by the idle gear increases with increasing angularspeed and increasing external excitation.Finally, a seven freedom rattle model of a certain automotive transmission is set up. According to theoretical studies, numerical simulation and experimental results, somemeasures are taken from the external stimulus, internal motivation, gear meshingdamping, and gear shaft torsional stiffness to control the rattle vibration and noise. Theresults show that improving the external motivation, internal motivation, gear meshingdamping and gear shaft stiffness can make the transmission rattle vibration and noise tobe effectively controlled.