Method for controlling an internal combustion engine

1. A method for controlling an internal combustion engine ( 1 ) by a turbocharger ( 12 ) provided with a turbine ( 13 ) and with a compressor ( 14 ) and comprising, furthermore, an intake manifold ( 4 ) and a number (W) of cylinders ( 3 ), which are connected to the intake manifold ( 4 ) and in which the air mass trapped in each cylinder ( 3 ) for each engine cycle can be adjusted in an independent manner through a respective intake valve by a valve actuation device with a variable opening, the control method comprising steps of:

determining the total target torque (C i _ objt ) required to be delivered for the operation of the internal combustion engine ( 1 );

determining a number (Wa) of active cylinders ( 3 ) to be controlled, in use, for the injection and the combustion; whereas a number (Ws) of cylinders ( 3 ) are not active and are not controlled for the combustion and the torque generation, but for sucking in an air mass;

determining the angle with which the intake valve has to be controlled by the valve actuation device with a variable opening of the number (Wa) of active cylinders ( 3 );

determining the angle with which the intake valve has to be controlled by the valve actuation device with a variable opening of the number (Ws) of inactive cylinders ( 3 ); and

controlling the internal combustion engine ( 1 ) as a function of the angle with which the intake valve has to be controlled by the valve actuation device with a variable opening of the number (Wa) of active cylinders ( 3 ) and as a function of the angle with which the intake valve has to be controlled by the valve actuation device with a variable opening of the number (Ws) of inactive cylinders ( 3 ).

2. A method according to claim 1 and comprising the further step of determining a target pressure (Pobj) of the intake manifold that is such as to guarantee the total target torque (Ci_objt) required to be delivered for the operation of the internal combustion engine ( 1 ).

3. A method according to claim 2 and comprising, in case of a supercharged internal combustion engine ( 1 ), the further step of determining the target supercharge pressure (Ptobj) that is such as to guarantee the target pressure (Pobj) of the intake manifold.

4. A method according to claim 1 and comprising the further steps of:

determining the target scavenge flow rate (Mscav), which represents the air quantity that optimizes the performances of the internal combustion engine ( 1 ), and determining the target scavenge mass (mscav) for each one of the number (Ws) of inactive cylinders ( 3 ); and

determining, by a first filling model, the angle with which the intake valve has to be controlled by the valve actuation device with a variable opening of the number (Ws) of inactive cylinders ( 3 ) as a function of the target scavenge mass (mscav).

5. A method according to claim 1 and comprising the further steps of:

determining the operating mode of the number (Ws) of inactive cylinders ( 3 ) among a plurality of possible operating modes; and

determining the angle with which the intake valve has to be controlled by the valve actuation device with a variable opening of the number (Ws) of inactive cylinders ( 3 ) as a function of the operating mode of the number (Ws) of inactive cylinders ( 3 ).

6. A method according to claim 1 and comprising the further steps of:

determining the combustion air mass (mobj) for each one of the number (Wa) of active cylinders ( 3 ) as a function of at least one of the efficiency of the spark advance applied and of the efficiency of the EGR and of the efficiency of the titer and as a function of the target torque (C i _ obj ) required to be delivered for the operation of the internal combustion engine ( 1 ) for each one of the active cylinders ( 3 ); and

determining, by a second filling model, the angle with which the intake valve has to be controlled by the valve actuation device with a variable opening of the number (Wa) of active cylinders ( 3 ) as a function of the combustion air mass (mobj) for each one of the number (Wa) of active cylinders ( 3 ) as a function of at least one of the efficiency of the spark advance applied and of the efficiency of the EGR and of the efficiency of the titer and as a function of the target torque (C i _ objt ) required to be delivered for the operation of the internal combustion engine ( 1 ) for each one of the active cylinders ( 3 ).

7. A method according to claim 5 and comprising the further steps of:

determining the operating mode of the number (Wa) of active cylinders ( 3 ) among a plurality of possible operating modes; and

determining the angle with which the intake valve has to be controlled by the valve actuation device with a variable opening of the number (Wa) of active cylinders ( 3 ) as a function of the operating mode of the number (Wa) of active cylinders ( 3 ).

8. A method according to claim 1 and comprising the further steps of:

determining a temporary number (Watemp) of active cylinders ( 3 ) to be controlled, in use, for the injection and the combustion as a function of the engine operation point;

determining the potential torque that can be delivered for the operation of the internal combustion engine ( 1 ) by the temporary number (Watemp) of active cylinders ( 3 );

comparing the potential torque that can be delivered for the operation of the internal combustion engine ( 1 ) by the temporary number (Watemp) of active cylinders ( 3 ) and the total target torque (C i _ objt ) required to be delivered for the operation of the internal combustion engine ( 1 ); and

determining the number (Wa) of active cylinders ( 3 ) as a function of the comparison between the potential torque that can be delivered for the operation of the internal combustion engine ( 1 ) by the temporary number (Watemp) of active cylinders ( 3 ) and the total target torque (C i _ objt ) required to be delivered for the operation of the internal combustion engine ( 1 ).

9. A method according to claim 8 and comprising, in an initial phase, the further steps of:

determining a reference number (Warif) of active cylinders ( 3 ) to be controlled, in use, for the injection and the combustion as a function of the engine operation point; and

initializing the temporary number (Watemp) of active cylinders ( 3 ) to be controlled, in use, for the injection and the combustion as a function of the engine operation point at the reference number (Warif) of active cylinders ( 3 ).

10. A method according to claim 8 and comprising the further step of causing the reference number (Warif) of active cylinders ( 3 ) to be equal to the temporary number (Watemp) of active cylinders ( 3 ), only in case the potential torque that can be delivered for the operation of the internal combustion engine ( 1 ) by the temporary number (Watemp) of active cylinders ( 3 ) is either of higher than and equal to the total target torque (C i _ objt ) required to be delivered for the operation of the internal combustion engine ( 1 ).

11. A method according to claim 9 and comprising the further steps of:

determining, in a preliminary adjustment and set-up phase, a deviation number (A) of cylinders ( 3 ) to be added to the combustion; and

updating the temporary number (Watemp) of active cylinders ( 3 ) by the deviation number (Δ) of cylinders ( 3 ), only in case the potential torque that can be delivered for the operation of the internal combustion engine ( 1 ) by the temporary number (Watemp) of active cylinders ( 3 ) is lower than the total target torque (C i _ objt ) required to be delivered for the operation of the internal combustion engine ( 1 ).

12. A control method according to claim 11 , wherein the deviation number (Δ) of cylinders ( 3 ) to be either of added to and subtracted from the combustion is equal to 2.

13. A control method according to claim 4 and comprising the further step of determining the target scavenge mass (Mscav), which represents the air quantity that optimizes the performances of the internal combustion engine ( 1 ), in a transient phase by the formula:

Mscav=Mscavrif ( C,n )+Δ(derivative(Ciobjt))

wherein:

Mscavrif (C,n): reference target scavenge mass, as a function of the engine operation point determined by the load and by the number of revolutions per minute; and

Ciobjt: total actual torque required to the drive shaft.

14. A method according to claim 1 and comprising the further step of injecting fuel into said number (Ws) of inactive cylinders ( 3 ).

15. A method according to claim 1 and comprising the further step of controlling said number (Ws) of inactive cylinders ( 3 ) for the combustion but not for the torque generation.