Patent ID: 8118707

Claim:
Method for controlling a friction clutch ( 3 ) and a continuously variable transmission ( 2 ) provided with a drive belt ( 23 ) wrapped around and in frictional contact with two variable pulleys ( 21 , 22 ) in a vehicular drive line, which method includes the step of activating the clutch ( 3 ) and the transmission ( 2 ) in relation to an engine torque (Te) generated by an engine ( 1 ) of the drive line, at least effecting that a torque level (Tc-max) transmissible by the clutch ( 3 ) is smaller than a torque level (Tt-max) transmissible by the transmission ( 2 ) and that a safety margin is realised between the torque level (Tt-max) transmissible by the transmission ( 2 ) and the engine torque (Te), wherein, said safety margin is adapted during operation by increasing or decreasing said safety margin at least in relation to and in proportion with one or more of: the value of a transmission ratio (Co/Cv) of the transmission ( 2 ); the inverse value of a rotational speed of the belt ( 23 ); and the inverse value of a current critical belt slip value (CBs) at which damage would occur to the transmission ( 2 ) to the extent that the transmission's operation is adversely affected thereby, and a normal force (Fn) is applied in the frictional contact between the belt ( 23 ) and the pulleys ( 21 , 22 ), which normal force (Fn) is determined by adding a margin to a nominal normal force (Fn-min) that would be required for the transmissible torque (Tt-max) of the transmission ( 2 ) to be equal to the engine torque (Te), which margin is maintained with the range of 1 to 7 kN during operation of the transmission ( 2 ).