Method and apparatus for controlling continuously variable transmission

Abstract

Method and apparatus for controlling a continuously variable transmission operatively connecting an engine and drive wheels of a vehicle, wherein a speed ratio of the transmission is controlled such that an actual engine speed coincides with a target engine speed. The method and apparatus comprise steps or devices for: determining a first target speed based on a currently required output of the engine; determining a second target speed based on a predetermined transmission efficiency of the transmission and on the first target speed, the second target speed being lower than the first target speed; determining a variation-resistant trigger speed based on a detected running speed of the vehicle, the trigger speed being within a speed range in which the engine provides a sufficient output necessary to permit desired acceleration of the vehicle; restraining a rate of variation in the speed ratio while the actual engine speed is raised from the trigger speed to the first target speed; and switching the target engine speed from the first target speed to the second target speed when the actual engine speed has been raised to the first target speed, whereby the engine speed is lowered from the first target speed to the second target speed. When the second target speed is reached, the second target speed is changed to the first target speed.