Method for controlling a continuously variable transmission and a transmission equipped with a control system for implementing said method

A method for controlling a continuously variable transmission,

• wherein the continuously variable transmission comprises an input shaft and an output shaft being rotatably arranged about a common central rotation axis, a ring wheel and a sun wheel being coaxially arranged with respect to the central rotation axis, and at least one pivotable planet wheel, a pivot angle of the planet wheel determining a transmission ratio of the continuously variable transmission,
• wherein the method comprises:
• operating the transmission through drill-free rolling of the at least one planet wheel on surfaces of the ring wheel and the sun wheel independently of the pivot angle of the planet wheel;
• clamping together the ring wheel, the at least one planet wheel and the sun wheel such that the ring wheel exerts a first normal force on the at least one planet wheel and the sun wheel exerts a second normal force on said planet wheel;
• operating the continuously variable transmission at a given input speed, a given transmitted torque and a given constant transmission ratio;
• applying a predefined static value of the first and second normal force by controlling said first and second normal forces, such that a condition of microslip is applied to rolling contacts between the at least one planet wheel and the ring wheel and the sun wheel;
• increasing or decreasing the pivot angle and thereby the transmission ratio;
• and
• while increasing or decreasing the pivot angle, each of the first and the second normal force is either maintained at the respective predefined static value, or is adapted by adding a force component to the respective predefined static values, wherein the force component is smaller than necessary for the respective normal force to maintain the microslip condition.