Patent ID: 9175630
Filing Date: 2015-11-03
Classification: F01L,F02D

Abstract:
1. An internal-combustion engine, comprising, for each cylinder: a combustion chamber; at least two intake ducts and at least one exhaust duct, which give out into said combustion chamber; at least two intake valves and at least one exhaust valve, which are associated to said intake and exhaust ducts and are provided with respective return springs that push them into a closed position; a camshaft for actuating the intake valves, by means of respective tappets; wherein each intake valve is controlled by the respective tappet against the action of the aforesaid return spring by interposition of hydraulic means including a pressurized-fluid chamber facing which is a pumping plunger connected to the tappet of the valve, said pressurized-fluid chamber being designed to communicate with the chamber of a hydraulic actuator associated to each intake valve; a single solenoid valve, associated to the intake valves of each cylinder and designed to set in communication said pressurized-fluid chamber with an exhaust channel in order to decouple the intake valve from the respective tappet and cause fast closing of the intake valves as a result of the respective return springs; and electronic control means, for controlling said solenoid valve so as to vary the instant of opening and/or the instant of closing and the lift of each intake valve as a function of one or more operating parameters of the engine, wherein the solenoid valve associated to each cylinder is a three-way, three-position solenoid valve, comprising: an inlet permanently communicating with said pressurized-fluid chamber and with an actuator of an intake valve; and two outlets communicating, respectively, with an actuator of a second intake valve and with said exhaust channel, said solenoid valve having the following three operating positions: a first position, in which the inlet communicates with both of the outlets so that the pressurized-fluid chamber, i.e., the actuators of both of the intake valves are set in a discharging condition, and the intake valves are both kept closed by their return springs; a second position, in which the inlet communicates only with the outlet connected to the actuator of the second intake valve and does not communicate, instead, with the outlet connected to the exhaust channel, so that the pressurized-fluid chamber is isolated from the exhaust channel, the actuators of both of the intake valves communicate with the pressurized-fluid chamber, and the intake valves are hence both active; and a third position, in which the inlet does not communicate with any of the two outlets, so that the aforesaid pressurized-fluid chamber is isolated from the exhaust channel, and the aforesaid first intake valve is active, whilst the second intake valve is isolated from the pressurized-fluid chamber and from the exhaust channel, said electronic control means being programmed for implementing, in one or more given operating conditions of the engine, a mode of control of said solenoid valve, in which: said solenoid valve is brought into said second position in an active phase of the tappet, in which the tappet tends to cause opening of the second intake valve so that said second intake valve opens; said solenoid valve is then brought from said second position into said third position when said active phase of the tappet in which said tappet governs opening of the second intake valve is still in progress, so that the hydraulic actuator of the second intake valve remains isolated and the second intake valve remains blocked in the open position in which it is; and said solenoid valve is kept in said third position even after the end of said active phase of the tappet, so that the second intake valve remains blocked in said open position even when the tappet no longer tends to keep it open.