Control system for belt-type continuously variable transmission

A control system for a belt-type continuously variable transmission which transmits an engine output to wheels by changing gears in a nonstep manner, the control system adapted to obtain a target gear change ratio and a target gear change ratio changing rate based on a vehicle speed and acceleration instruction information, obtain a driven pulley required axial thrust required for motive power transmission in response to a transmission input torque and a gear change ratio without causing a belt slip, set the driven pulley required axial thrust as a driven pulley target axial thrust, set an axial thrust required by a driven pulley for changing the gear change ratio to the target gear change ratio at the target gear change ratio changing rate by use of the driven pulley target axial thrust as a driving pulley target axial thrust, and conduct speed change control by controlling an actuation hydraulic pressure based on target supplied hydraulic pressure set in response to the driven pulley target axial thrust and the driving pulley target axial thrust,nthe control system comprising a correction section adapted to predict a hydraulic pressure decreasing amount likely to occur in a prescribed time at a current hydraulic pressure changing rate based on a hydraulic pressure value of the actuation hydraulic pressure detected by a hydraulic pressure sensor, predict an actuation hydraulic pressure likely to occur in the prescribed time based on the predicted hydraulic pressure decreasing amount, and conduct a correction to increase supplied hydraulic pressure if the predicted actuation hydraulic pressure is lower than a minimum required hydraulic pressure that is a predetermined surplus pressure for the actuation hydraulic pressure.

A computer-implemented method for controlling a belt-type continuously variable transmission which transmits an engine output to wheels by changing gears in a nonstep manner, the method comprising:nobtaining a target gear change ratio and a target gear change ratio changing rate based on a vehicle speed and acceleration instruction information;obtaining a driven pulley required axial thrust required for motive power transmission in response to a transmission input torque and the gear change ratio without causing a belt slip;setting the driven pulley required axial thrust as a driven pulley target axial thrust;setting an axial thrust required by a driven pulley for changing the gear change ratio to the target gear change ratio at the target gear change ratio changing rate by use of the driven pulley target axial thrust as a driving pulley target axial thrust;conducting speed change control by controlling an actuation hydraulic pressure based on target supplied hydraulic pressure set in response to the driven pulley target axial thrust and the driving pulley target axial thrust;predicting a hydraulic pressure decreasing amount likely to occur in a prescribed time at a current hydraulic pressure changing rate based on a hydraulic pressure value of the actuation hydraulic pressure detected by a hydraulic pressure sensor;predicting an actuation hydraulic pressure likely to occur in the prescribed time based on the predicted hydraulic pressure decreasing amount, andcorrecting supplied hydraulic pressure to be increased if the predicted actuation hydraulic pressure is lower than a minimum required hydraulic pressure that is a predetermined surplus pressure for the actuation hydraulic pressure.