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

摘要

An internal-combustion engine with two intake valves 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 of the system with an exhaust channel. The solenoid valve is a three-way, three-position solenoid valve, comprising an inlet permanently communicating with the pressurized-fluid chamber and with the hydraulic actuator of an intake valve, and two outlets communicating, respectively, with the actuator of the other intake valve and with said exhaust channel. The solenoid valve has a first position, in which the inlet communicates with both of the outlets, a second position, in which the inlet communicates only with the aforesaid outlet connected to the actuator of an intake valve and does not communicate, instead, with the outlet connected to the exhaust channel, and a third position, in which the inlet does not communicate with any of the two outlets.

主权项

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 tappets of the at least two intake valves, a pressurized-fluid chamber being designed to communicate with a 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 valves from their respective tappets 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, said engine being characterized in that 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 the hydraulic actuator of a first of the at least two intake valves; and two outlets communicating, respectively, with the hydraulic actuator of the second of at least to intake valves 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 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 pressure chamber is isolated from the exhaust channel, the actuators of both of the intake valves communicate with the pressure 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 pressure chamber is isolated from the exhaust channel, and the aforesaid first intake valve is active, whilst the second intake valve is isolated from the pressure chamber and is consequently inactive.