Internal-combustion engine, with system for variable actuation of the intake valves provided with a three-way electric valve having three levels of supply current, and method for controlling said engine

摘要

An internal-combustion engine includes a three-way, three-position control valve with an inlet communicating with a pressurized-fluid chamber and with a 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 control 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 outlet connected to the actuator of an intake valve and does not communicate, with the outlet connected to the exhaust channel, and a third position, in which the inlet does not communicate with the two outlets. The control valve has an electric actuator supplied only at three different values of electric current to bring the valve into the three positions.

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 open 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 a respective tappet of said tappets against the action of the 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 electrically actuated or electromagnetically actuated control 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 control 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, the control valve associated to each cylinder is a three-way, three-position valve, comprising:
an inlet permanently communicating with said pressurized-fluid chamber and with the actuator of an intake valve; andtwo outlets communicating, respectively, with the actuator of the second intake valve and with said exhaust channel, said control 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, and the intake valves are both kept closed by the 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; anda 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 from the exhaust channel, said control valve having an electric actuator configured for being supplied only at three different values of electric current:
a first value of current for bringing the control valve into the second position and keeping it in said second position;a second value of peak current, higher than said first value, for bringing said control valve into said third position; anda third value of hold current, lower than said second peak value and higher than said first value, for keeping said control valve in said third position once it has been brought into said third position.