Ratio selection method for a continuously variable transmission during deceleration by braking

A ratio selection method for a continuously variable transmission (CVT) for a vehicle during deceleration, comprising:

• determining at least one of a distance of a brake pedal travel and a rate of deceleration of the vehicle, wherein rate of deceleration of the vehicle is expressed as a negative value;
• determining a Current Actual Speed Ratio of the CVT when at least one of the distance of the brake pedal travel exceeds a predetermined distance and rate of deceleration of the vehicle is below a predetermined valve;
• determining an amount of Available Speed Ratio Change (Δr), wherein:
• Δr=(the Minimum Under-drive Speed Ratio)−(the Current Actual Speed Ratio);
• determining a Current Ratio Change Capability (Current-{dot over (r)}) of the CVT;
• determining a Predictive Ratio Change Capability (Predictive-{dot over (r)}), wherein:
• (Predictive-{dot over (r)})=[(Current-{dot over (r)})+K]/2,
• where K is a Ratio Change Capability at an idle engine rpm;
• calculating a Time to Reach the Minimum Under-drive Ratio (tUD), wherein (tUD) includes the Available Speed Ratio Change (Δr) divided by the Predictive Ratio Change Capability (Predictive-{dot over (r)});
• calculating a Predicted Velocity of the Vehicle (vPr) using (tUD);
• determining a Desired Speed Ratio of the CVT using the Predicted Velocity of the Vehicle (vPr);
• and
• actuating the CVT to the Desired Speed Ratio.

A system for implementing a method for selecting a speed ratio for a continuously variable transmission (CVT) of a vehicle during braking, comprising:

• a vehicle speed sensor configured to detect the velocity of the vehicle;
• a CVT speed ratio sensor;
• a brake pedal position sensor;
• at least one powertrain operating factor sensor;
• and
• a transmission control module (TCM) in communication with the vehicle speed sensor, CVT speed ratio sensor, and the at least one powertrain operating factor sensor, where in the TCM is configured to:
• determine a distance of a brake pedal travel;
• determine a Current Actual Speed Ratio of the CVT when the distance of the brake pedal travel exceeds a predetermined distance;
• determine an amount of Available Speed Ratio Change (Δr), wherein Δr=(minimum under-drive speed ratio)−(Current Actual Speed Ratio);
• and
• determine a Desired Speed Ratio of the CVT.