Mode transition control in a CVT with fixed gear functionality

A continuously variable transmission (CVT) assembly comprising:

• an input member having an input speed;
• an output member having an output speed;
• a variator assembly having a pair of variator pulleys and an endless rotatable drive element which connects and transfers torque between the pair of variator pulleys, including a drive pulley connected to the input member and a driven member connected to the output member, wherein the drive and driven pulleys each include a pair of sheaves;
• a first pulley actuator operable to move one of the pair of sheaves of a respective one of the drive and driven pulleys to thereby change a speed ratio of the CVT;
• a plurality of sensors collectively operable for measuring the input and output speeds of the CVT and a linear displacement of each of the drive pulley and the driven pulley;
• and
• a controller in communication with the plurality of sensors, wherein the controller is programmed to calculate a speed ratio and a geometric ratio of the CVT during a friction drive mode of the CVT using the measured input speed, output speed, and linear displacements, to calculate a relative slip of the drive and driven pulleys during a friction drive mode of the CVT using the calculated speed ratio and the geometric ratio, to control the relative slip during a friction drive mode until the relative slip is below a calibrated speed limit or within a calibrated speed range, via transmission of an actuator control signal to the first pulley actuator, and to command a fixed gear/positive engagement mode of the CVT via positive engagement control signals to the CVT until the relative slip is zero.

A method for controlling a mode transition in a vehicle having a continuously variable transmission (CVT) with a friction drive mode and a fixed gear/positive engagement drive mode, the method comprising:

• measuring an input speed of a variator assembly of the CVT, an output speed of the variator assembly, and a linear displacement of each of a drive and a driven pulley of the variator assembly;
• calculating, via a controller, a speed ratio and a geometric ratio of the CVT during the friction drive mode of the CVT using the measured input speed, output speed, and linear displacements;
• calculating a relative slip of the drive and driven pulleys using the speed ratio and the geometric ratio;
• transmitting, when the relative slip is within a calibrated speed range, an actuator control signal from the controller to at least one of a pair of pulley actuators, each of which connected to the other via an endless rotatable drive element and is operable to move a respective moveable sheave of the drive and driven pulleys to thereby reduce the calculated relative slip until the relative slip is below a calibrated slip limit or within a calibrated speed range;
• and
• transmitting positive engagement control signals from the controller to the CVT, when the relative slip is below the calibrated speed limit or within the calibrated speed range, until the relative slip is zero to thereby transition the CVT to the fixed gear/positive engagement mode.