Research On The Viscous Coupling For Two-motor Driven Electric Vehicle

The development of electric vehicles is an effective method to solve the problemof energy shortage and environmental deterioration in the future. Electric vehicle can bedivided into two catagories: centralized driving and independent driving. For independentdriving electric vehicles, the mechanical transmission system is simplified, drivingefficiency improves and vehicle performance can be improved by controlling the torque ofevery driving wheel, but power coupling devices is needed to avoid the decline of vehicledynamic performance when the anti-slip control works. In order to solve this problem, thispaper will match a power coupling device for two-motor driven vehicle, and do rearch onthe viscous coupling. This paper is supported by Natural Science Foundation of China.Firstly, the structure of the viscous coupling and how it works are analyzed. Basedon Newton inner friction law, the transfered torque calculation model is established. Toabtain the accurate expression of shear stress, the Navier-Stokes equation is solved, sothe model is modified. Then the influence of the number of inner plate and outer plates, thesilicone oil viscosity, the distance of two plates, rotating speed difference, to the trasferdtorque is studied, which provides the theory support for the design of the structure ofviscous coupling.Secondly, the process of hump phenomenon for the viscous coupling is described indetail. The relationship between Weissenberg effect of non-Newtonian fluid and the humpphenomenon is studied. Then temperature and pressure in the viscous coupling arecalculated when the hump phenomenon occurs.Thirdly, a simplified geometric model of the internal flow field of viscous coupling isestablished by the Solidworks. After meshing, the viscous coupling’s internal flow field iscalculated by numerical method by the Computational Fluid Dynamics analysis softwareFluent. The simulation results report velocity distribution and pressure distribution, so thestate of the flow field is abtained.Finally, based on the analysis about working characteristics of viscous coupling, therelated theories and design experience, the structural parameter of viscous coupling isdetermined. According to the testing system, test bench is established. Experimental dataproves that the viscous coupling match the requirement. After that, the silicone oil viscosity and the distance of two plates are changed separately, the experimental data by bench testhave a better agreement with the calculation results. It shows that the theoretical model isquite accurate.