Internal-combustion engine with variable actuation of the intake valves and self-adaptive control of the air-fuel ratio with supervision of the control functions

An internal-combustion engine, comprising:

• at least one intake valve for each cylinder, provided with elastic means tending to push the valve towards a closed position;
• at least one camshaft for controlling said intake valves by means of respective tappets;
• and
• an electronically controlled hydraulic system for variable actuation of the intake valves, said system including:
• a pressurized fluid chamber set between each of said tappets and a respective intake valve, said pressurized fluid chamber being designed to be connected to an exhaust channel by means of a passage controlled by a solenoid valve so that when said solenoid valve is opened the intake valve is uncoupled from the respective tappet and is kept closed by said elastic means;
• and
• electronic control means for controlling each solenoid valve so as to vary the time and/or travel of opening of the respective intake valve as a function of the operating conditions of the engine;
• wherein said engine moreover comprises means for detecting the air-fuel ratio, designed to detect and/or calculate the effective value of the air-fuel ratio with which the engine is operating, to enable functions of self-adaptive control of the air-fuel ratio by the electronic control means,
• said engine being characterized in that the aforesaid electronic control means are programmed for performing, at least once in the life of the engine, an activity of supervision of the functions of self-adaptive control of the air-fuel ratio, said activity of supervision including:
• activating a late-opening actuation mode of the intake valves, wherein the intake valves are opened with a pre-set delay with respect to the conventional cycle determined by the geometry of the cam;
• in said late-opening mode, detecting the error represented by the difference between the effective value of the air-fuel ratio as detected by said means for detecting the air-fuel ratio and a theoretical value of the ratio estimated by said electronic control means;
• and
• storing the variation that must be applied to the value of the crank angle used by said electronic control means in controlling said actuation system in order to cause the value of the air-fuel ratio estimated by said electronic control means to coincide with the aforesaid effective value of the air-fuel ratio, on the basis of identification of a constant value of the ratio existing between a variation in the value of the crank angle and the error in the estimation of the air-fuel ratio when the system operates in late-opening mode,
• said electronic means being programmed for always applying throughout the subsequent life of the engine the aforesaid corrective value of the crank angle in controlling the system of actuation of the intake valves.