Patent ID: 8677747

Claim:
A method for controlling an internal-combustion engine ( 1 ) supercharged by a turbocharger ( 12 ) and including a turbine ( 13 ) and compressor ( 14 ), said control method comprising steps of: establishing a predetermined lower-limit speed of the turbocharger ( 12 ) and predetermined higher-limit speed of the turbocharger ( 12 ); calculating a reduced lower-limit speed (N rid — inf ) of the turbocharger ( 12 ) according to the predetermined lower-limit speed of the turbocharger ( 12 ) and an absolute temperature (T o ) upstream of the compressor ( 14 ); calculating a reduced higher-limit speed (N rid — sup ) of the turbocharger ( 12 ), according to the predetermined higher-limit speed of the turbocharger ( 12 ) and absolute temperature (T o ) upstream of the compressor ( 14 ), that is higher than the reduced lower-limit speed (N rid — inf ) of the turbocharger ( 12 ); determining an over-speed interval of the turbocharger ( 12 ) included between the reduced lower-limit speed (N rid — inf ) and reduced higher-limit speed (N rid — sup ) of the turbocharger ( 12 ); calculating a current reduced-limit speed; controlling the turbocharger ( 12 ) so as to bring the reduced-limit speed back to a value substantially no greater than the reduced lower-limit speed (N rid — inf ) substantially every time a value of the current reduced-limit speed is detected and included within the over-speed interval; establishing in a preliminary adjustment and set-up phase a first threshold value (S OV — 1 ); and controlling the turbocharger ( 12 ) so as to bring the reduced-limit speed back to a value substantially no greater than the reduced lower-limit speed (N rid — inf ) after a time interval, which is substantially equal to the first threshold value (S OV — 1 ), has elapsed from a moment in which a value of the current reduced-limit speed is detected and included within the over-speed interval.