| Limited Slip Differential(LSD) is a new high-technique for improving the performance of vehicle. It gets more and more extensive application in the international car product. At our country, research and develop work about it also begins to arouse more notice, and doesn't achieve suitable self-exploitation product in market. This paper has completed develop of JA1020 VLSD and JA1020LSD and set up a LSD model for computing torque transmitted with the help of key scientific research item from national economy-trade committee. we have completed some research tests and validated the accurate and believable of design-compute and theory model. Meanwhile nine-freedom whole vehicle model for analyzing vehicle's controllability and stability is set up. At last, by way of computer simulation and comparison analysis using of the vehicle models with different differentials brought out upward, we have validated the improving of vehicle controllability and stability because of LSD and practicability of the vehicle model set up. Main contents as follows:First,The paper educes calculation equations for shearing torque transmitted by VLSD from the research theory of two parallel infinite plate's shearing torque produced by the relative turning between them. Afterwards, the paper analyzes all kinds of factors that influence the characteristic of transferring torque of VLSD 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 VLSD and the working temperature of it is the main outside factors influencing the shear torque of VLSD. Second, By using of electrical -control driveline test-rig, we complete assembly test of LSD and VLSD. It mainly measures how the characteristics of limited torque outputted change when viscosity of silicon oil, distance of vane, initial temperature and filling ratio change. We can know that the lower of silicon oil working temperature, the higher of silicon oil viscosity, the smaller of vane distance and the bigger of the difference of rotate speeds, the higher the limited torque of outputted by VLSD will become, by analyzing the test data and test curve. This model describes that the working temperature of it is the main outside factor influencing the shear torque of LSD. That simulating result agrees with test result validates the correctness and validity of LSD assembly model set up. 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 vehicle" 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 then, the vehicle's controllability stability has been analyzed by using of computer simulation.With the comparison of vehicle with LSD and vehicle with ordinary differential, the paper finds the obvious improving of limited torque on vehicle's controllability and stability, and the feasibility of math model brought out. The effects on vehicle's controllability stability of LSD mainly consist in the decrease of yaw velocity, slide acceleration, and vehicle roll angle, and the increase of understeer and steering force etc. These results indicate that the stability and security of the vehicle when turning is effectively improved, and in some degree the vehicle's ride-comfortability is improved too. Meanwhile it just brings a little effect on fuel-economic in accepting degree. But the slip torque just brings a little bad effect on fuel economy. On the other hand, The effects on vehicle's instantaneous characteristic LSD consist in ahead of peak time, decrease of excess and steady state. Th... |
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