Design Analysis And Test Research For Planetary Traction Deceleration Bearing Of Automotive In-wheel Motor

In view of the active demand of the high efficiency and high power density reducer for the automotive high power density in-wheel motor,combined with the self-designed automotive in-wheel motor and the transmission characteristics of the traction drive,this paper put forward a new bearing device—the planetary traction deceleration bearing,which could both have the function of the speed reducer(Decreasing speed and increasing torsion)and the bearing(Providing radial support).Then,theoretical calculation,simulation analysis and experimental work were carried out to design and research it,which was used to discuss the practicability that planetary traction deceleration bearing could apply to automotive high power density in-wheel motor.The main work accomplished in this paper is as follows:(1)Combined with the self-designed automotive in-wheel motor and the transmission characteristics of the traction drive,on the basis of the interference fit traction drive device,a new bearing device was innovatively put forward named planetary traction deceleration bearing,which could both have the function of the speed reducer(Decreasing speed and increasing torsion)and the bearing(Providing radial support).Then,the fundamental design was developed for it.(2)In order to prevent pitting fatigue and to accurately calculate the assembling interference value,the finite element contact characteristics analysis was carried out and the general method of the finite element contact characteristics analysis was proposed.Based on the validation of the finite element contact algorithm,the traction pair contact characteristics were accurately calculated and the calculation results were analyzed.(3)In order to improve the reliability of the planetary traction deceleration bearing and to coordinate the contradiction of the large interference value and the fatigue life,the interference value design was carried out.Then,the influence of the outer ring and the rolling element thickness on the radial deformation(i.e.,the interference value)and the stress was obtained.Finally,a suitable interference value was determined,which could also prevent bending fatigue fracture and contact fatigue failure.(4)The finite element strength analysis of the planetary traction deceleration bearing was developed,which shows that it meets the fatigue strength requirement under the rated working condition.Then,the finite element static radial stiffness of the planetary traction deceleration bearing was carried out,which shows that the static radial stiffness can be basically kept unchanged under the 1~10 times rated radial static load and the input axis has a very high rotation precision.Moreover,the finite element modal analysis of the planetary traction deceleration was developed,which shows that the natural frequency is far greater than the system characteristic frequency and resonance phenomenon will not appear.(5)To research the transmission characteristic of planetary traction deceleration bearing,the transmission mechanism was first researched.Then,combined with the elastohydrodynamic lubrication theory and the Evans-Johnson rheological mode,a mathematical model and an analysis method were proposed to accurately calculate the transmission characteristics.Finally,the results show that the traction pair can meet the full fluid film lubrication under the rated condition,which can avoid the immediate contact between driving rollers to prevent frictional wear.Moreover,the change rule of the transmission power and the transmission efficiency with the sliding rate was revealed,and the influence of the traction pair length on transmission characteristics was discussed.(6)The transmission efficiency test of planetary traction deceleration bearing was carried out.Then,the change rule of the transmission efficiency with different rotation rate and torque was obtained.Moreover,the good precision of the transmission characteristics theoretical calculation model was proved in low transmission power and good heat dissipation,and the result deviation analysis was carried out.Finally,the best traction oil for planetary traction deceleration bearing was obtained.