| The electric wheel is also known as the in-wheel motor,where the power devices,transmission and braking devices are integrated.The electric motor simplifies the structure of the electric car,improving the transmission efficiency and reducing the noise during the car driving process.Simplified chassis structure is conducive to increase passenger space,and provides the guarantee for electronization and intelligentization of the automotive chassis system.Because of the high transmission efficiency and flexible control of the structural characteristics,the electric wheel is regarded as the ultimate driving mode of electric vehicle,and has become one of the hot and difficult research of electric vehicles.Planetary gear driving is an important mechanical slowdown mode for vehicle electric wheels.Its function is to maintain high efficiency and power density in high speed condition,while provide smooth torque and climbing performance in low speed condition.Planetary gears have been widely applied in electric wheels because of its unique advantages.In consideration of the complexity of planetary gear splash lubrication experiment,fluid simulation analysis can reduce the cost of experimental workload.On the basis of the given parameter,numerical simulation of the fluid with a computer is equivalent to a numerical experiment.In the design of planetary gear transmission system,the initial immersion oil depth setting is an experiential value.The magnitude of its numerical value directly affects the amount of oil splashed during the rotation of the planetary gear,and the planetary transmission efficiency.The simulation of the planetary gears’ splash lubrication can obtain macroscopic flow field information in the early stage of the design,and assist in finding the balance between the initial oil immersion depth and the transmission efficiency.The equilibrium point can direct the planetary gear to determine numerical value of the initial immersion oil depth.Fluid simulation technology with its advantages of low cost and accurate result is widely used in engineering field such as fluid mechanical design.This paper will study relevant laws of planetary gear splash lubrication by using the method of fluid simulation.The thesis includes the following main contents.(1)Briefly introduce the development situation of vehicle electric wheel at home and abroad,conduct comparative analysis on the two driven ways of electric wheel about its main structure,advantages and disadvantages.The necessity of design planetary gear transmission within vehicle electric wheel has been explained,and the gear splash lubrication simulation research situation at home and abroad has also been discussed,which provides technical route for the research on simulation of planetary gear splash lubrication.(2)Introduce NGW planetary gear reducer structure and its transmission characteristics,based on CAD/CAE technology,through the analysis and calculation,planetary gear reducer which can be installed within the narrow wheel has been designed.By combining theoretical calculation with CAE software analysis,the reliability of the planetary gear transmission system has been validated.(3)Based on the theory of Computational Fluid dynamics(CFD),carry on numerical simulation for a given oil immersion depth and speed of the planetary transmission,Fluid distribution,Fluid velocity,Fluid pressure are chosen as the main line of analyzing the internal flow field of planetary transmission.The dynamic change law of flow field has been got.The obtained oil stirring power through planetary transmission splash lubrication simulation after fluid finally gets stable is compared with the theoretical calculation value,which has verified the reliability of the simulation model.(4)Aimed at different speed and initial immersion depth conditions,planetary gear splash lubrication will be simulated to study.The influence rule of the rotational speed and the initial oil immersion depth on the internal flow field is compared in order to select the important parameters of the planetary gear lubrication system,and ensure the entire transmission system can work well under different conditions.(5)Through the analysis of the sources about power loss of planetary gear,the mathematical model of transmission efficiency in transmission system can be established.Using the mathematical relationship between transmission efficiency and the initial oil immersion depth and CFD numerical simulation software,the equilibrium point can be found to direct to determine the value of the initial immersion oil depth when design planetary gear transmission lubrication system. |
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