Internal-combustion engine having a system for variable actuation of the intake valves, provided with an electrically actuated valve having two ways and three positions

摘要

An internal-combustion engine includes a system for variable actuation of intake valves, including a control valve for each cylinder, which controls communication of a pressurized-fluid chamber with a discharge channel. The control valve has at least three different positions, namely, a first completely open position, a second partially open position, and a third completely closed position. Electronic control means are programmed for keeping the control valve in its closed position in operating stages in which the intake valve must remain coupled to the respective cam and for bringing the control valve from its completely closed position to its partially open position or to its completely open position in operating stages in which the intake valve must be uncoupled from the respective cam, selection between the first position and said second position of the control valve being made as a function of one or more operating parameters of the engine.

主权项

1. An internal-combustion engine, comprising for each cylinder of the engine:
a combustion chamber; at least one intake duct and at least one exhaust duct opening out into said combustion chamber; at least one intake valve and at least one exhaust valve associated to said intake and exhaust ducts and provided with respective return springs that push the at least one intake valve and the at least one exhaust valve toward a closed position; and a camshaft for actuating the intake valves by means of respective tappets; wherein said at least one intake valve is governed by a respective tappet of the tappets against an action of the return spring by interposition of hydraulic means including a pressurized-fluid chamber, facing which is a pumping plunger connected to the respective tappet of the valve, said pressurized-fluid chamber being capable of communicating with a chamber of a hydraulic actuator associated to said at least one intake valve; a single electrically actuated control valve associated to said at least one intake valve of each cylinder and capable of setting said pressurized-fluid chamber in communication with a discharge channel in order to uncouple said at least one intake valve from the respective tappet and cause rapid closing of said at least one intake valve by action of the respective return spring; electronic control means, for controlling said control valve to vary an instant of opening and/or the instant of closing and a lift of each intake valve as a function of one or more operating parameters of the engine, the electrically actuated control valve associated to each cylinder being a two-way valve having at least three different operating positions, comprising: a first operating position in which the control valve is completely open; a second operating position in which the control valve is only partially open; and a third operating position in which the control valve is completely closed, and said electronic control means programmed for: keeping said control valve in said third, completely closed, position in operating stages in which said at least one intake valve must remain coupled to the respective cam, bringing said control valve from said third, completely closed, position to said second, partially open, position or to said first, completely open, position in operating stages in which said at least one intake valve must be uncoupled from the respective cam, the selection between said first position and said second position of the control valve being made as a function of one or more operating parameters of the engine.