| As one of the key components in the automobile power transmission system,the noise and vibration problems of the transmission have a great impact on the NVH performance of the vehicle.The noise generated by gear rattle has a wide frequency band,and the sound pressure level has a step phenomenon,which is more likely to cause troubles and complaints from people in the car.Therefore,it has become a major noise problem and has gradually attracted the attention of major automobile manufacturers.In addition,the dual clutch transmission(DCT)has an increased number of rattle gears under the pre-selected gear strategy,making the DCT gear rattle problem more prominent.Based on this,this paper takes a certain type of DCT with gear rattle problem as the research object,and studies its gear rattle problem by combining test and simulation.The main research contents are as follows:1.The mechanism and conditions of gear rattle are studied,and the rattle form and threshold theory are expounded.The influence mechanism of transmission output fluctuation characteristics,backlash,time-varying meshing stiffness(TVMS),drag torque and idle inertia on gear rattle is theoretically analyzed.Summarize several commonly used gear rattle objective evaluation index.2.The rattle state of each gear pair of the DCT under different gear positions is analyzed;The rattle dynamics model of single gear pair considering the factors such as TVMS,drag torque,backlash and oil film force is established.The TVMS is calculated by potential energy method.The oil film force is introduced into the model by considering the entrainment and squeeze effect of lubricating oil between backlash.Through the single gear pair dynamics model and the simplification of the transmission structure,the dynamic model of DCT multi-gear rattle is built.3.The DCT rattle bench test was carried out.The vibration acceleration sensor was used to collect the vibration signals of DCT shell under different gear states.The holes were drilled at the corresponding shell of each loose gear and the magnetoelectric speed sensor was placed to collect the angular acceleration signal of the loose gear,the effects of different pre-selected states on DCT shell vibration and gear rattle are studied by time domain and frequency domain analysis.The vibration of the shell caused by the rattle is more severe;the accuracy of the DCT multi-gear rattle dynamic model is verified by the test results.4.The influence of pre-selected gears on the dynamic response of each gear pair of DCT is analyzed,and the impact strength of each gear pair is analyzed based on the gear rattle index.The influence of different parameters on the gear relative displacement,FFT,phase trajectory and other gear rattle dynamic responses was studied.The research results show that with the increase of the fluctuation amplitude of the input angular acceleration,the gear pair gradually transitions from no rattle to single-sided rattle,and finally changes to double-sided rattle,the motion form of gear pair changes from regular motion to irregular and chaotic motion,and the rattle intensity gradually increases.The drag torque has a restraining effect on the gear rattle,and the drag torque is negatively correlated with the rattle intensity.The inertia of the idle gear has little effect on the rattle form,but reducing the moment of inertia can reduce the knock strength;reducing the backlash can also reduce the gear rattle strength.Based on the law of parameter influence,a multi-parameter and multi-level orthogonal test is designed,and the parameters of the gear pair of 6th gear with obvious rattle under the pre-selected 4th gear are optimized. |
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