摘要:
An internal combustion engine for motor-vehicles, includes a system for variable actuation of the intake valves of the engine having a solenoid valve controllable between a closed condition and an open condition wherein it places a pressurized fluid chamber in communication with an exhaust chamber, with the aim of decoupling the intake valve from the respective tappet and causing the quick closing of the intake valve due to the respective return spring. The solenoid valve has a valve element with a cylindrical body having a first conical surface portion and a second conical surface portion. The conical surface portions are defined by the axially opposite ends of a circumferential groove formed on the valve element. The first conical surface portion cooperates with the valve seat. The other conical surface portion has an outer diameter substantially identical to the diameter of the annular edge defining the valve seat.
摘要:
A fuel injection system for an internal combustion engine, comprising: at least one fuel electroinjector; and one electronic control unit designed to supply the fuel electroinjector, in a fuel injection phase in an engine cylinder, with at least a first electrical command to perform a pilot fuel injection, and a second electrical command to perform a main fuel injection. The first and second electrical commands are separated in time by an electrical dwell time such that the main fuel injection starts without interruption with respect to the pilot fuel injection. The electrical dwell time between the first and second electrical commands belongs to an electrical dwell time range in which the total fuel amount injected in the pilot and main fuel injections in a fuel injection phase in an engine cylinder is substantially constant.
摘要:
A metering servovalve for a fuel injector of an internal combustion engine has an electro-actuator and a fixed valve body, which defines a control chamber communicating with an inlet and with an outlet channel. The outlet channel has at least one calibrated restriction and exits through the lateral surface of an axial stem, on which a sleeve slides, in a substantially fluid-tight manner, to open/close the outlet channel and so vary the pressure in the control chamber. The outlet channel is closed by an end portion of the sleeve that is elastically deformable in a radially outward direction, under the thrust of the fuel pressure, to increase the diameter at which the seal against the valve body is formed, with respect to a non-deformed state, and to generate a radial unbalancing force on the sleeve upon opening when the outlet channel is closed.
摘要:
The injector comprises a balanced metering servovalve to control a rod for the opening/closing of a nozzle. La servovalve has a valve body with a control chamber radially delimited by a tubular portion and fitted with an outlet passage that is opened/closed by an axially movable shutter. The servovalve is also integral with an axial stem, provided with a lateral surface, through which the outlet channel exits. The shutter is coupled to the stem in an axially sliding manner and, when it closes the outlet passage, it is subjected to substantially null axial fuel pressure. The outlet passage has a calibrated segment distanced from the shutter and close to a bottom wall of the control chamber. The calibrated segment is carried by an element fixed to the valve body in correspondence to an axial segment of the outlet passage.
摘要:
A fuel-injection system for an internal-combustion engine has at least one fuel injector with a fuel-metering servo valve provided with an open/close element, which is movable in response to the action of an electric actuator; and an electronic control unit which issues to the electric actuator two electrical commands, one for carrying out a pilot injection and one for carrying out a main injection; the two electrical commands being separated by an electrical dwell time such that the main injection starts, without solution of continuity with the pilot injection, when an open/close needle for carrying out fuel injections into a cylinder of the internal-combustion engine remains at a lift value in which the fuel flow rate is negligible; in particular, the second electrical command is issued during a rebound of the open/close element on the valve seat.
摘要:
A fuel injection system for an internal combustion engine, comprising: at least one fuel electroinjector; and one electronic control unit designed to supply the fuel electroinjector, in a fuel injection phase in an engine cylinder, with at least a first electrical command to perform a pilot fuel injection, and a second electrical command to perform a main fuel injection. The first and second electrical commands are separated in time by an electrical dwell time such that the main fuel injection starts without interruption with respect to the pilot fuel injection. The electrical dwell time between the first and second electrical commands belongs to an electrical dwell time range in which the total fuel amount injected in the pilot and main fuel injections in a fuel injection phase in an engine cylinder is substantially constant.
摘要:
The injector comprises a balanced metering servovalve for controlling a rod for opening/closing a nebulizer. The servovalve has a valve body having a control chamber provided with an outlet passage that is opened/closed by an axially mobile open/close element. The open/close element is made of a single piece with a bushing separate from an armature plate of an electromagnet. The bushing is coupled to a stem in an axially slidable way for closing an exhaust duct in communication with the outlet passage The open/close element is kept in a closed position by a spring that acts upon the bushing through an intermediate body connected thereto. The armature plate can be displaced with respect to the bushing between a flange of the intermediate body and a shoulder of the bushing, for eliminating the rebounds of the open/close element upon closing of the servovalve.
摘要:
A solenoid valve comprises a first mouth for an inlet of a working fluid and a second mouth and a third mouth for an outlet of the working fluid. The valve has a first operating position in which a passage of fluid from the first mouth to the second mouth and the third mouth is enabled, a second operating position in which a passage of fluid from the first mouth to only one of the second and third mouths is enabled, and a third operating position in which the passage of fluid from the first to the second mouth and the third mouth is disabled.
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.
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.