Noise Analysis And Optimization Of High Speed Wheel Reducer Used In Electric Vehicle

As the main development way of the future automobile industry,electric vehicle has been researched by automobile companies and many scholars across the globe.Electric vehicle eliminates the engine and exhaust system which are the largest noise resource in conventional internal combustion vehicle,then the whine noise which produced by high-speed gear transmission system becomes the main source of noise.Therefore,this work focuses on a wheel reducer for electric vehicle by establishing the radiation noise calculation and analysis model of the wheel reducer.In addition,this paper studied the effects of macro geometry parameters of the gear transmission system and gear modification on dynamic characteristics of the gear transmission system and the radiation noise of the wheel reducer housing.Moreover,this research can bring important theory significance and great engineering values for designing the high-speed wheel reducer gear transmission system and reducing the vibration of the system.The main contents of this dissertation are shown as follows:(1)The transmission structure of a wheel reducer for electric vehicle is analyzed,by using finite element and lumped parameter method to establish the dynamic model of the gear transmission system which contains three parts: gear meshing element,shaft element and bearing element.The Lagrange’s energy method and the Timoshenko beam theory are used to derive the dynamic equations of gear meshing element and shaft element respectively.Moreover,a fixed stiffness and damping are used to simplify the bearing element,then combining all the dynamic equations of each parts to get the dynamic equations of the system.Based on the LMS Virtual Lab software,a spider element was established at each bearing seat to get the vibration response of the gearbox surface,and acoustics finite element model was established to calculate the radiation noise.Finally,the process of calculating radiation noise of the gearbox housing was summarized.(2)The time-varying internal and external excitations of the wheel reducer were calculated and analyzed,and the Runge-Kutta method was used to solve the differential equations of the system to calculate the vibration response of the system under rated conditions.Constraint modal analysis was performed on the wheel reducer housing to obtain the front 10 orders modal frequencies and modes shapes.Combined the vibration response of the gearbox housing,the acoustic finite element method was used to calculate the A-weighted sound pressure level radiated noise of the gearbox housing.It can be found that the maximum radiated noise value happens at 1600 Hz,which is close to the sixth-order modal frequency of the housing,and the gearbox housing mainly radiates noise in the z direction through the upper gearbox.(3)The influence of pressure angle and helix angle on the dynamic characteristics of the transmission system and the radiation noise of the gearbox housing are studied,and the results show that when the pressure angle is 17° or the helix angle is 24° of the output stage gear pair,the vibration acceleration of the transmission system is reduced,and the radiation noise of the wheel reducer housing can be significantly reduced;When the axial contact ratio is close to an integer,the transmission system has smaller peak-peak value of transmission error and vibration.(4)Based on the rated working conditions,two kinds of gear modification for gear pairs are proposed to study the effects of different modification methods on gear meshing characteristics.Scheme one used crown modification of lead modification and liner modification of profile modification which can reduce the peak-peak value of transmission error of gear pairs and improve the gear deviation load;Crown modification of both lead and profile modification were used in scheme two,and the peak-peak value of transmission errors of gear pairs is lower than scheme one.Moreover,the gear pairs have better meshing characteristics.When the transmission system with the scheme two gear modification,the radiated noise of the wheel reducer housing was reduced by 9dB.