Research On The Mechanism And Application Of Viscous Limited Slip Differential

Limited Slip Differential(LSD) is a new technique for improving the performance of vehicle. It get more and more extensive application in the international car field. But at our country, it developes not much, and doesn't achieve suitable product in practice. This paper makes mainly researches on the application for LSD in vehicle. Main contents as follows: The paper educes calculation equations for shearing torque transmitted by viscous couple from the research method of two parallel infinite plate's shearing torque produced by the relative turning between them. Afterwards, the paper analyzes the factors that influence the characteristic of transferring torque of viscous couple and gets the calculation model for computing the shear torque of VLSD, with inclusion of all factors that have effect on the characteristic. This model describes that the difference of rotate speed of two axle of viscous couple and the working temperature of it is the main outside factors influencing the shear torque of VLSD. And so the paper simplifies the heat-transfered process and establishes the calculation equations to analyze the temperature of viscous couple making use of method of calorifics. Therefore, the instantaneous characteristic of viscous couple can be described as the function of the two inputing-speed and working time of viscous couple. Making use of this model, we can analyze the working property of VLSD with the assistance of computer simulation. In addition, this paper brings out a method that can be used to calculate the time and press that the viscous couple begins to come out torque amplification. On the other hand, with a view to analyze the controllability and stability by virtue of the method of system simulation, by analyzing the vehicle in dynamics during its turning, this paper establishes a "three-wheel"model by linearization method for analyzing the controllability and stability of rear-driving vehicle with LSD. This model may be used to analyze the effect of limited torque on vehicle's controllability and stability. And then the paper establishes a simulation model for computer based on the mathematic model explained upward. And so, the application issues, such as, the effect of limited torque of LSD on the vehicle's stability, the matching degree between the limited torque and the vehicle's stability, can be analyzed by using of computer simulation. With the comparison of vehicle with LSD, whose characteristic of limited torque is measured out in Test Rig, and vehicle with ordinary differential, the paper finds the obvious effect of limited torque on vehicle's controllability and stability. Main representation of it is, in one side, the decrease of yaw velocity, slide acceleration, and vehicle roll angle, on the other side, the increase of understeer and steering force. These results indicate that the stability and security of the vehicle is improved, and the vehicle's ride-comfortability is improved too. But the slip torque is bad for steering force. By way of computer simulation using of the model brought out upward, this paper analyzes the vehicle's steady state cornering, slaiom steer, and the property of step response. Meanwhile, the result of the simulation, comparing with the result of vehicle's test, represent that the model brought out in this paper is accurate and believable. We can ayalyze the influence of the LSD on the vehicle's controllability and stability and the matching between them preferably. At last, the paper brings forward the basic principle of friction disc LSD based on the forthgoing analyzation. In addition, this paper analyzes the variation of controllability and stability of the vehicle assembled with VLSD, and finds that the VLSD has less influence on the vehicle's controllability and stability. The research developed in this paper will promote the study of VLSD in our country more penetrately, and improve the accuracy of the theoretic analyzation and calculation in Viscous Limited Slip Differential(VLSD). At same time, the research developed in this paper will make people know more about LSD, and urge them to the research of this new technique. This research will improve the matching degree between the LSD and vehicle's controllability and stability in the design of LSD. Therefore, this research willaccelerate the coming forth of the suitable domestic LSD product. In addition, the attempt of this paper in analyzing the vehicle's dynamics by virtue of computer simulation will promote the application of this technique in vehicle field.