Abstract
Abstract
In this paper, the pressure characteristics for a metal belt-type independent pressure-control-type continuously variable transmission (CVT) are investigated, and a remedy to reduce the pressure fluctuations in the steady state is proposed. From the experiments, pressure fluctuations are observed for some secondary pressure range in the underdrive speed ratios. In order to analyse the pressure characteristics, dynamic models of the hydraulic control system including the CVT variator are obtained. Using the dynamic models, the parameters that affect the pressure fluctuations are investigated. From the simulations, it is found that the change in the hydraulic stiffness is the main reason for the pressure fluctuations. Based on the stiffness analysis, modification of the secondary control valve supply port notch is proposed to decrease the hydraulic stiffness gradient of the supply line from the secondary control valve to the CVT variator. From the simulation and the experiments, it is found that pressure fluctuations can be reduced effectively by this modification of the hydraulic stiffness.
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