| Noise performance is the critical factor affecting the core competitiveness of the vehicle and it depends highly on the gearbox.As shown by a large number of studies,the noise of vehicles’ gearbox is mainly caused by the vibration of the gearbox’s gear pair which is closely related with the geometric error of gear.This paper aims to study the quantitative relation between geometric error of gears with gearbox noise and thus provide theoretical and practical guidance for the geometric accuracy optimization design of transmission gear.In view of the purpose above,the paper works from the following aspects:(1)The gear surface model taking geometric error into consideration is established.It raises an assumption based on the actual situation of production and the gear measuring center: both the tooth profile error and the spiral line error of the gear would remain unchanged when they are measured in different positions of the tooth surface.On the basis of this assumption,it constructs a tooth surface model considering the geometric error regulated in GBT10095.1-2008.(2)The meshing analysis is carried out on the tooth surface considering geometric error.This paper gets the transmission error,bearing transmission error and timevarying meshing stiffness through TCA(Tooth Contact Analysis)and LTCA(Lord Tooth Contact Analysis)with geometric error taken into account.The orthogonal simulation experiment is designed based on TCA,which leads to the qualitative conclusion: The tooth profile angle deviation of pinion,the tooth profile shape deviation of pinion,the helix angle deviation of pinion and the tooth profile angle deviation of large gear exert the greatest influences on the gear transmission error.Besides,it discusses the influences of gear geometric error on gear bearing transmission error and gear time-varying meshing stiffness based on LTCA.As shown by the comparison between the ideal gear and the orthogonal test No.9 in terms of the geometric error of tooth profile,the time-varying meshing stiffness amplitude of the gear increases by8μm/N and the amplitude of bearing transmission error rises by 0.9μm.(3)The vibration simulation is performed for the gear model considering geometric error.This paper builds a gear pair vibration model with bending-torsionvibration six degree of freedom and a two-stage transmission model with eight degree of freedom,analyzes the stress of gear shaft to get the time-varying support force of the gear shaft and calculates the no-load knock of the gear through energy method.Meanwhile,it calculates the gear vibration considering four errors with the accuracy ranging between level 3 to level 9,including of the pinion’s tooth profile angle deviation,the pinion’s tooth profile shape deviation,the pinion’s helix angle deviation and the pinion’s tooth profile angle deviation based on the meshing time-varying stiffness of the gear pair obtained through the load-bearing contact analysis and the load-bearing transmission error of the gear pair.In accordance with the comparative results,the main frequency response of each support point rises by 113.51 N,89.13 N,43.36 N and 13.32 N respectively and the vibration of the gear pair is becoming increasingly violent with the decline of geometric accuracy.(4)Simulation analysis considering geometric error for gearbox is carried out.It compares the acoustic simulation results and the existed test results to verify the rationality of the dynamic model,which shows that the gear noise calculated through this method is slightly larger than the actual noise,but they follow the same change trend in general.Therefore,the method applied by this paper is basically correct.Then,it carries out noise simulation on the gearbox by taking the shaft support response calculated above as the excitation to get the gearbox noise considering geometric error.The work of predicting gearbox noise based on gear geometric error is thus completed.(5)This paper carries out optimization design for the reducer of an existed newenergy vehicle and the gearbox of an existed traditional internal combustion engine.With the slightly degraded noise performance of the reducer,it brings down the manufacturing cost of the reducer;the no-load knock of the traditional combustion is reduced and the noise performance of the gearbox is improved by raising the pitch accuracy.At last,the natural frequency of the box is obtained through modal analysis and the geometric error form of natural frequency vibration is retrieved,based on which the form of tooth profile error that will lead to such frequency vibration is obtained.It shall pay special attention to the tooth profile error of such form in the production process.To sum up,this paper first proposes a method to predict gearbox noise through tooth surface modeling,contact analysis,vibration simulation and acoustic simulation by taking geometric error into consideration.Then,it discusses the influences of gear geometric error on each link.Reliability of this method is verified through the comparison with existed experimental data.Furthermore,it optimizes the gearbox noise based on the method put forward in the paper. |
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