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Study of the Prediction Method for Maximum Traction Coefficient
Abstract:
This report proposes a rheological model and a thermal analysis model for oil films, which transmit power through a variator, as a prediction method for the maximum traction coefficient, and then describes the application and verification of this method.
The rheological model expresses the conditions inside the contact ellipse using a combination of viscosity and plasticity.
The thermal analysis model for oil films was confirmed by comparison of previously obtained temperatures directly measured from the traction contact area of the four-roller experimental apparatus [1]. The measurement used a thin-film temperature sensor and the consistency between the calculated and measured values was verified in the estimation model by reflecting the precise thermal properties of the thin film. Most values were consistent with the calculated values for the middle plane local shear heating model inside the oil film. However, under some conditions, the values were closer to those calculated for homogeneous shear. Based on these results, this paper proposes a calculation method that combines both heating models within the contact ellipse.
In addition, the variator in a continuously variable transmission (CVT) was verified for the first time by using a test box to take direct temperature measurements from the transmission contact area in the CVT. This test verified the precision of the thermal analysis model, including the spin motion.
Finally, the maximum traction coefficient was estimated using these calculation models and compared with measured values.