Internal-combustion engine having a system for variable actuation of the intake valves, provided with three-way solenoid valves, and method for controlling said engine

摘要

An internal-combustion engine with two intake valves (7A, 7B) for each cylinder is provided with a system for variable actuation of the intake valves, comprising a single solenoid valve for each cylinder that controls communication of the pressurized-fluid chamber (C) of the system with an exhaust channel (23). The solenoid valve is a three-way, three-position solenoid valve, comprising an inlet (i) permanently communicating with the pressurized-fluid chamber and with the hydraulic actuator of an intake valve (7B), and two outlets (u1, u2) communicating, respectively, with the actuator of the other intake valve (7A) and with said exhaust channel. The solenoid valve has a first position (P1), in which the inlet communicates with both of the outlets, a second position (P2), in which the inlet communicates only with the aforesaid outlet (u1) connected to the actuator of an intake valve (7A) and does not communicate, instead, with the outlet (u2) connected to the exhaust channel (23), and a third position (P3), in which the inlet (i) does not communicate with any of the two outlets (u1, u2). There is envisaged an operating mode in which said solenoid valve is brought a number of times, within the aforesaid active phase of the tappet, first into one of said second and third positions (P2, P3), then into the other of said second and third positions (P2, P3), and then into its first position (P1), so that each of the two intake valves (7A, 7B) associated to each cylinder of the engine performs two or more subcycles of complete opening and closing during the active phase of the respective tappet, the subcycles of the two intake valves (7A, 7B) being differentiated from one another.