摘要:
An engine includes at least one cylinder, a first intake valve and a second intake valve associated with the cylinder, to control a flow of intake air from a first intake duct and a second intake duct, respectively. The two intake ducts communicate with a common intake manifold, so as to receive air at the same pressure. During the intake stage, in each cylinder operating cycle, initially an opening and closing movement of only the first intake valve is activated, while the second intake valve remains closed and, subsequently, an opening and closing movement of only said second intake valve is activated, while the first intake valve remains closed. In this way, the two air flows at the same pressure entering the cylinder give rise to a high turbulent kinetic energy, to the advantage of combustion efficiency and reduction of harmful exhaust emissions.
摘要:
An atomizer of a fuel electro-injector is equipped with a nozzle and a valve needle having a head, which is coupled to a sealing seat of the nozzle, and stem, which engages an inner seat of the nozzle; the stem and the nozzle define an annular passageway with a chamber that axially terminates at the sealing seat; the stem has an intermediate portion coupled in an axially sliding manner in the inner seat and defining a plurality of channels, the outlets of which are arranged on the annular chamber; the sealing seat and the head of the valve needle define a discharge section, which is annular and has a width that increases as the opening stroke of the valve needle proceeds; the ratio between the depth and the outer chord of the minimum cross-section of the channels is greater than or equal to two.
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, including a single solenoid valve for each cylinder that controls communication of a pressurized-fluid chamber of the system with an exhaust channel. The solenoid valve is a three-way, three-position solenoid valve, including 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 the 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 aforementioned 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.
摘要:
An internal combustion engine includes an electro-hydraulic system for variable actuation of intake valves where each cylinder has two intake valves, associated with two intake conduits. A first conduit is generates within the cylinder a tumble motion of airflow introduced therein, when the intake valve associated thereto is at least partially opened. The second intake conduit generates within the cylinder a swirl motion of airflow introduced therein when the second intake valve is at least partially opened. A controller of controls one or more control valves to open only one of the intake valves of each cylinder in a condition of reduced engine operation, below a predetermined load and/or a predetermined speed of the engine, and to always open both intake valves in the remaining conditions of engine operation. The first intake valve is the only valve to be opened in the reduced engine operation condition.
摘要:
An actuating system of an engine valve comprises a movable member, for example, in the form of a master piston controlled by a cam of a camshaft. A slave piston is hydraulically controlled by the master piston by means of a volume of pressurized fluid, to open said engine valve against the action of a return spring. The system also comprises an auxiliary device for applying an additional force to the engine valve to keep the engine valve in a closed position. The auxiliary device is configured or controlled in such a way that the total force tending to keep the engine valve in its closed position varies during each rotation cycle of the cam. The total force is higher at least in one part of the rotation cycle of the cam wherein the engine valve must remain in its closed position, and is, instead, reduced at least in one part of the rotation cycle of the cam wherein the engine valve is not in its closed position.
摘要:
A system for variable actuation of an engine valve of an internal-combustion engine includes a master piston and a slave piston, driven by the master piston. A control valve controls a communication of a volume of a pressurized fluid with a lower pressure environment, which is connected to a fluid accumulator, and an electronic control unit controls the electrically operated control valve. A device for dampening pressure oscillations is connected to the volume of pressurized fluid and includes an additional volume adapted for receiving fluid from the volume of pressurized fluid only when, following upon oscillations of the pressure in the volume of pressurized fluid, the pressure exceeds a maximum threshold value, which is higher than a mean pressure value that is set up in the volume of pressurized fluid when the master piston drives the slave piston in normal operating conditions.