| Pure electric vehicle reducer is one of the core components of today’s electric vehicle drive train,which transmission efficiency and working reliability of the reducer affect the mileage of electric vehicles.Because of the small size and high integration of the electric vehicle reducer,the heat dissipation area is small and the heat dissipation conditions are poor.Excessive temperature has a great influence for the transmission performance of the reducer.According to research that the amount of lubricating oil in the reducer directly affects the surface temperature of the various components and the transmission efficiency of the reducer.If the amount of lubricating oil is small,the reducer is in a state of underlubrication,and the tooth surface temperature cannot be taken away in time.The tooth surface temperature is high,but the churning is small.If the amount of lubricating oil is large,the reducer is in a fully lubricated state,and the tooth surface temperature is relatively low,but the oil stirring loss is relatively large.Therefore,the overall thermal analysis of the electric vehicle reducer system and the study of its optimal lubricating oil quantity on this basis have important academic value.This article first analyzes the heat generation of each element in the reducer,establishes a theoretical calculation model for the power loss of each element,and analyzes the influencing factors of various losses at the same time.The study found that the operating conditions and operating temperature of the reducer have a greater impact on its energy loss.Secondly,the thermal resistance of each element of the reducer was studied.According to the heat transfer route of the reducer,the heat transfer mode between the elements was divided into heat conduction and heat convection,and a theoretical calculation formula was established.Then,the moving particle semi-implicit method(MPS)was applied to numerically analyze the lubricating oil flow field distribution of the gearbox under different lubricating oil quantity and working conditions.And the calculation method of the volume ratio of the oil-gas mixture was proposed to make the calculation of convective heat transfer coefficient more accurate,which lays the foundation for building a more accurate thermal network model of the reducer.Then the reducer was divided into nodes reasonably and the nodes are divided into heat generating nodes and thermal resistance nodes.Based on the principle of heat transfer between nodes,the secondary development module AMESet software was used to develop the thermal network model of the reducer.Then the reducer test bench was used to test its transmission efficiency and oil temperature,and compare it with the calculation result of the thermal network model.As results that the calculation error of the model are within 5%,indicating that the thermal network model has a high calculation accuracy and can be used for late research.Finally,combined with the calculation results of the thermal network model,the influence of lubricating oil quantity on the steady-state temperature field of the reducer was analyzed with ANSYS software.And combined with the low-temperature efficiency analysis of the reducer,it was determined that the optimal lubricating oil volume is 0.4L when the reducer has high comprehensive transmission performance. |
