Abstract
Abstract
In this paper, an algorithm to improve the fuel economy of a metal belt continuously variable transmission (CVT) vehicle by CVT shift speed control is suggested. By rearranging the CVT shift dynamic equation, it is found that the CVT shift speed depends on the line pressure as well as on the primary pressure. CVT shift speed maps are constructed to evaluate the influence of the line pressure on the shift speed. To obtain a target shift speed, an algorithm to calculate the line pressure is presented. In order to estimate the shift speed and the hydraulic loss, dynamic models of the line pressure control valve and the ratio control valve are obtained by considering the CVT shift dynamics and validated by experiments. It is found from the simulation results that fuel economy can be improved by 2 per cent in spite of the increased hydraulic loss due to the increased line pressure.
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