Patent ID: 7509803

Claim:
A method ( 1 ) for controlling the speed of rotation of a turbosupercharger ( 7 ) in an internal-combustion engine ( 2 ) of a motor vehicle comprising: a compressor ( 9 ), a turbine ( 8 ) for driving the compressor ( 9 ) in rotation under the action of the exhaust gases of the engine ( 2 ); and a wastegate valve ( 12 ) for regulating the flow rate of the exhaust gases provided at input to the turbine ( 8 ) for controlling the speed of rotation of the turbine ( 8 ) itself as a function of an objective supercharging pressure (P OB ) which indicates the value of the supercharging pressure that, on the basis of an objective map of the engine and of a set of parameters of engine is required at output from said compressor ( 9 ); said method being characterized in that it comprises the steps of: establishing a limit speed of rotation (N tc ) of the turbosupercharger ( 7 ); and during control of the speed of rotation of the turbine ( 8 ) performed through said wastegate valve ( 12 ), implementing the following steps: measuring the pressure (P AMB ) of the air taken in at input by the compressor ( 9 ); determining the mass flow rate (Q AH ) of the compressor ( 9 ); calculating, through a predetermined map ( 15 a ) that characterizes operation of the compressor ( 9 ) and as a function of the preset limit speed of rotation (N tc ), of the measured air pressure (P AMB ), and of the mass flow rate (Q AH ), a limit supercharging pressure (S P1 ), which is correlated to the air pressure obtainable at output from the compressor ( 9 ) when the turbine ( 8 ) turns at a speed substantially equal to said pre-set limit speed (N tc ); verifying whether the required objective supercharging pressure (P OB ) satisfies a pre-set relation with said calculated limit supercharging pressure (S P1 ), said preset relation being satisfied when said required objective pressure (P OB ) is higher than said limit supercharging pressure (S P1 ); and in the case where said relation is satisfied, actuating said wastegate valve ( 12 ) for controlling the speed of rotation of the turbine ( 8 ) as a function of the limit supercharging pressure (S P1 ) so as to limit the speed of rotation of said turbosupercharger ( 7 ) to a value substantially equal to said preset limit speed (N tc ): in the case where said relation is not satisfied, actuating said wastegate valve ( 12 ) for controlling the speed of rotation of the turbine ( 8 ) as a function of the objective supercharging pressure (P OB ) so as to achieve a supercharging corresponding to the objective pressure (P OB )itself.