| The main reducer hypoid gear is one of the important components of the automobile transmission system and its churning resistance torque directly affect the vehicle transmission efficiency and the fuel consumption.Therefore,the analysis of the churning transient flow field distribution of the main reducer hypoid gear and the influence of the key parameters on the churning power losses were analyzed,aiming to explore the formation mechanism of the churning resistance torque and the investigation of drag reduction,which has a clear theoretical value and practical engineering guidance significance for the research of automobile energy saving and consumption reduction.Firstly,combined with the ParticleWorks gear churning numerical simulation and theoretical analysis,the composition and proportion of the churning resistance was verified and obtained.Reference to the empirical formula,the influence of the viscosity-temperature relationship and the additional bolt structure was considered,and the theoretical calculation models of the churning resistance torque of the bolt and the main reducer gear were established.Secondly,the numerical simulation model of three-dimensional churning of the main reducer hypoid gear was established.With the model,the three-dimensional transient flow field distribution,dynamic pressure field and velocity field as well as vorticity distribution were studied.The influence law of the rotation speed,rotation direction,immersion depth,temperature and bolt structure on the churning power losses were investigated.A two-dimensional calculation model reflecting the detailed flow field structure was established for analyzing the formation mechanism of the bolt churning resistance torque.The research shows that:(a)The rotation speed has the greatest influence on the churning power,the immersion depth is second,followed by the rotation direction,and the temperature influence is relatively minimal;(b)the bolt structure resulting in greater pressure drag in the lubricant distribution area at the left end.On the other hand,the bolt structure will cause a strong vortex motion of the flow field during the operation of the gear,forming a chaotic vorticity band distribution in the lubricant distribution area at the left end,which result in additional churning resistance torque and churning power losses.Thirdly,on this basis,combined with the research,a structural optimization scheme of changing the bolted model to the laser welding model was proposed.The finite element analysis of the laser welding model was completed to verify weld strength,and a lightweight scheme was proposed.In addition,the dynamic pressure,vorticity and churning resistance torque as well as churning power of the two models before and after structural improvement were compared and analyzed,and the theoretical calculated and simulated values of the bolt churning resistance torque are compared and analyzed,which verifies the accuracy of the two models.The results show that at different rotation speeds,the laser welding model can reduce the dynamic pressure of 1.64%~6.5% and reduce the churning power losses of 5.56%~8.20%.Finally,the bench efficiency test and the whole vehicle fuel consumption test of the two main reducer gear models were completed.The bench efficiency test shows that at 40 °C and 80 °C,the average transmission efficiency of the laser welding model is 0.32%~0.96% and 0.5%~1.56% higher than the bolted model respectively,which shows that the transmission efficiency of rear axle can be effectively improved.The whole vehicle fuel consumption test shows that the NEDC fuel consumption of the laser welding model is reduced by 0.087L/100 km on average compared with the bolt model,which indicates that the laser welding model can achieve energy saving and consumption reduction.The correctness of the laser welding structure improvement scheme and the flow field numerical simulation analysis was verified. |
