Method for controlling the fuel supply in a cylinder of a four-stroke internal combustion engine with controlled ignition

1. Method for controlling the fuel injection in an four-stroke internal combustion engine ( 1 ) with controlled ignition comprising at least one cylinder ( 2 ), an intake manifold ( 5 ) that feeds fresh air into the cylinder ( 2 ) and an injector ( 10 ) that injects indirectly fuel into the cylinder ( 2 ); the control method comprises the steps of:

determining a desired air/fuel ratio (λ DES );

determining, before the exhaust phase, a first forecast (P PR-1 ) of the intake manifold suction pressure during the suction phase by means of a first forecast algorithm that uses previous measures (P M ) of the intake manifold suction pressure;

determining, before the exhaust phase, an initial programming of fuel injection as a function of the desired air/fuel ratio(λ DES ) and of the first forecast (P PR-1 ) of the intake manifold suction pressure during the suction phase;

controlling, until the end of the exhaust phase, the fuel injection by piloting the injector ( 10 ) according to the initial programming of fuel injection,

determining a measure (P M-S ) of the intake manifold suction pressure at the end of the exhaust phase;

determining, at the end of exhaust phase, a second forecast (P PR-2 ) of the intake manifold suction pressure during the suction phase by means of a second forecast algorithm that also uses the measure (P M-S ) of the intake manifold suction pressure at the end of the exhaust phase;

determining, at the end of the exhaust phase, a final programming of fuel injection as a function of the desired air/fuel ratio (λ DES ), of the second forecast (P PR-2 ) of the intake manifold suction pressure during the suction phase and of the initial programming of fuel injection; and

controlling, starting from the suction phase, the fuel injection by piloting the injector ( 10 ) according to the final programming of fuel injection.

2. Control method according to claim 1 , wherein the first forecast algorithm is identical to the second forecast algorithm.

3. Control method according to claim 1 , wherein the first forecast algorithm is different from the second forecast algorithm.

4. Control method according to claim 3 , wherein the second forecast algorithm makes a linear extrapolation of a measure (P M-E ) of the intake manifold suction pressure at the end of the expansion phase and a measure (P M-S ) of the intake manifold suction pressure at the end of exhaust phase to determine the second forecast (P PR-2 ) of the intake manifold suction pressure during the suction phase.

5. Control method according to claim 1 , wherein the phase for determining, before the exhaust phase, the initial programming of fuel injection comprises the additional steps of:

determining, before the exhaust phase, a first estimate of the mass (M AIR-1 ) of air to be sucked into the cylinder ( 2 ) during the suction phase as a function of the first forecast (P PR-1 ) of intake manifold suction pressure during the suction phase;

calculating, before the exhaust phase, a first mass (M FUEL-1 ) of fuel to be injected as a function of the first estimate of the mass (M AIR-1 ) of air to be sucked into the cylinder ( 2 ) during the suction phase and of the desired air/fuel ration (λ DES ); and

determining, before the exhaust phase, a first opening engine angle (A O1 ) of the injector ( 10 ) and a first closing engine angle (A C1 ) of the injector ( 10 ) as a function of the first mass (MFUEL 1 ) of fuel to be injected.

6. Control method according to claim 1 , wherein the step of determining, at the end of exhaust phase, the final programming of fuel injection comprises the additional steps of:

determining at the end of the exhaust phase, a second estimate of the mass (M AIR-2 ) of air to be sucked into the cylinder ( 2 ) during the suction phase as a function of the second forecast (P PR2 ) of the intake manifold suction pressure during the suction phase;

calculating at the end of exhaust phase, a second mass (M FUEL-2 ) of fuel to be injected as a function of the second estimate of the mass (M AIR-2 ) of air to be sucked into the cylinder ( 2 ) during the suction phase and of the desired air/fuel ratio (λ DES ); and

determining, at the end of the exhaust phase, a second opening engine angle (A O2 ) of the injector ( 10 ) and a second closing engine angle (A C2 ) of the injector ( 10 ) as a function of the second mass (M FUEL-2 ) of fuel to be injected and of the initial programming of fuel injection.

7. Control method according to claim 1 , wherein the initial and final programming of fuel injection comprise a single injection performed mainly between the exhaust and the suction phase, determined by a combination of initial and final programming, and with a closing engine angle as central as possible between the beginning of the suction phase and a determined margin from the actual end of the suction phase.

8. Control method according to claim 1 , wherein the initial and final programming of the fuel injection comprise two different injections: a first injection performed during the exhaust phase and determined solely by the initial programming to inject a fraction of a first mass (MFUEL 1 ) of fuel to be injected determined from the initial programming and a second injection performed during the suction phase and determined by the difference between the initial programming and final programming.

9. Control method of fuel injection in a four-stroke internal combustion engine ( 1 ) with controlled ignition comprising at least one cylinder ( 2 ), an intake collector ( 5 ) that feeds fresh air into the cylinder ( 2 ) and an injector ( 10 ) that injects the fuel directly into the cylinder ( 2 ), the control method comprises the steps of:

determining a desired air/fuel ratio (λ DES );

determining, before the suction phase, a forecast (P PR ) of the intake manifold suction pressure during the suction phase by a forecast algorithm that uses previous measures (P M ) of the intake manifold suction pressure;

determining, before the suction phase, an initial programming of the fuel injection as a function of the desired air/fuel ratio (λ DES ) and of the forecast (P PR ) of the intake manifold suction pressure during suction phase;

controlling, until the end of the suction phase, the fuel injection by piloting the injector ( 10 ) according to the initial programming of the fuel injection,

determining a measure (P M-A ) of the intake manifold suction pressure at the end of the suction phase;

determining, at the end of the suction phase, a final programming of the fuel injection as a function of the desired air/fuel ratio (λ DES ) ratio, of the measure of the intake manifold suction pressure (P M-A ) at the end of the suction phase and of the initial programming of the fuel injection; and

controlling, starting from the compression phase, the fuel injection by piloting the injector ( 10 ) according to the final programming of the fuel injection;

wherein the forecast algorithm makes a linear extrapolation of a measure (P M-E ) of the intake manifold suction pressure at the end of the expansion phase and of a measure (P M-S ) of the intake manifold suction pressure at the end of exhaust phase to determine the forecast (P PR ) of intake manifold suction pressure during the suction phase.

10. Control method according to claim 9 , wherein the phase for determining, before the suction phase, the initial programming of the fuel injection comprises the additional steps of:

determining, before the suction phase, a first estimate of the mass (M AIR-1 ) of air to be sucked into the cylinder ( 2 ) during the suction phase as a function of forecast (P PR ) of the intake manifold suction pressure during the suction phase;

calculating, before the suction phase, a first mass (M FUEL-1 ) of fuel to be injected as a function of the first estimate of the mass (M AIR-1 ) of air to be sucked into the cylinder ( 2 ) during the suction phase and of the desired air/fuel ratio (λ DES ); and

determining, before the exhaust phase, a first opening engine angle (A O1 ) of the injector ( 10 ) and a first closing engine angle (A C1 ) of the injector ( 10 ) as a function of the first mass (M FUEL1 ) of fuel to be injected.

11. Control method according to claim 9 , wherein the phase for determining, at the end of the suction phase, the final programming of fuel injection comprises the additional steps of:

determining, at the end of the suction phase, a second estimate of the mass (M AIR-2 ) of air that has actually been sucked into the cylinder ( 2 ) during the suction phase as a function of the measure (P M-A ) of the intake manifold suction pressure at the end of the suction phase;

calculating, at the end of the suction phase, a second mass (M FUEL-2 ) of fuel to be injected as a function of the second estimate of the mass (M AIR-2 ) of air that has actually been sucked into the cylinder ( 2 ) during the suction phase and of the desired air/fuel ratio (λ DES ); and

determining, at the end of the suction phase, a second opening engine angle (A O2 ) of the injector ( 10 ) and a second closing engine angle (A C2 ) of the injector ( 10 ) as a function of the second mass (M FUEL-2 ) of fuel to be injected and of the initial programming of fuel injection.

12. Control method according to claim 9 , wherein the initial and final programming of fuel injection comprise a single injection performed mainly between the suction phase and the compression phases, determined by a combination of the initial and final programming, and with a closing engine angle as central as possible between the beginning of the compression phase and a determined margin from the ignition engine angle.

13. Control method according to claim 9 , wherein the initial and final programming of the fuel injection comprise mainly two different injections: a first injection performed during the suction phase and determined entirely by the initial programming to inject a fraction of a first mass (M FUEL1 ) of fuel to be injected determined by the initial programming and a second injection performed during the compression phase and determined by the difference between the initial programming and final programming.

14. Control method according to claim 9 and comprising the further steps of:

determining, in a phase prior to the suction phase, a first estimate of the mass (M AIR-DES-1 ) of the desired air to be sucked into the cylinder ( 2 ) during suction phase;

determining, in a phase prior to the suction phase, a first forecast (P PR-1 ) of the intake manifold suction pressure during the suction phase by a first forecast algorithm that uses previous measures (P M ) of the intake manifold suction pressure;

determining, in a phase prior to the suction phase, an initial programming of the suction of air as a function of the first estimate of the mass (M AIR-DES-1 ) of the desired air to be sucked into the cylinder ( 2 ) during the suction phase and of the first forecast (P PR-1 ) of the intake manifold suction pressure during the suction phase;

controlling, until the end of the exhaust phase, the aspiration of air into the cylinder ( 2 ) by piloting the control device ( 13 ) for the implementation of the intake valve ( 6 ) according to the initial programming of the suction of air;

determining a measure (P M-S ) of the intake manifold suction pressure at the end of exhaust phase;

determining, at the end of the exhaust phase, a second forecast (P PR-2 ) of the intake manifold suction pressure during the suction phase by a second forecast algorithm that also uses the measure (P M-S ) of the intake manifold suction pressure at the end of exhaust phase;

determining, the end of the exhaust phase, a final programming of air suction as a function of the second forecast (P PR-2 ) of the intake manifold suction pressure during the suction phase and of the initial programming of air suction; and

controlling, starting from the suction phase, the suction of air into the cylinder ( 2 ) by piloting the control device ( 13 ) for the implementation of the intake valve ( 6 ) according to the final programming of air suction.