Internal combustion engine, with a system for variable actuation of the intake valves provided with improved solenoid valves, and solenoid valve for this engine

Internal combustion engine, comprising:

• a combustion chamber,
• at least one intake conduit and at least one exhaust conduit ending up in said combustion chamber,
• an intake valve and an exhaust valve associated to said intake conduit and said exhaust conduit and each provided with respective return springs which push the valve towards a closed position,
• a camshaft for actuating the intake valves, through respective tappets,
• wherein each intake valve is controlled by the respective tappet against the action of the abovementioned return spring by hydraulic means including a pressurized fluid chamber on which there is faced a pumping piston connected to the tappet of the valve,
• a solenoid valve controllable between a closed condition and an open condition, wherein said solenoid valve places said pressurized fluid chamber in communication with an exhaust channel for decoupling the intake valve from the respective tappet and causing the quick closing of the intake valve due to the respective return spring,
• electronic control means, for controlling said solenoid valve to vary the opening instant and/or the closing instant and/or the lift of the intake valve as a function of one or more engine operative parameters,
• wherein said solenoid valve comprises:
• a valve body with a cylindrical inner cavity, at least one inlet opening communicating with said pressurized fluid chamber, formed radially through said body and ending up on said cylindrical cavity, and at least one outlet opening defined by an end of said cylindrical cavity which ends up on an end surface of the valve body,
• a valve seat, formed on said valve body or on an annular element fixed in said valve body, said valve seat being defined by a concentric annular edge with said cylindrical cavity,
• a valve element having a valve element body with an outer surface having a first surface portion and a second surface portion, said first surface portion and said second surface portion being substantially conical and having opposite conicities, said valve element body being cylindrical and slidably mounted within said cylindrical cavity of the valve body between a first position wherein said first surface portion is in contact with said valve seat, so as to prevent a communication between said inlet opening and said outlet opening, and a second position wherein said first surface portion is spaced from said valve seat, so as to establish the communication between said inlet opening and said outlet opening, said second portion having an outer diameter substantially identical to a diameter of said annular edge defining the valve seat,
• spring means for returning the valve element towards one of said first and second position, and an electromagnet which can be activated to move the valve element towards the other position,
• said electromagnet comprising a solenoid mounted on the valve body and a moveable anchor controlled by the solenoid and associated to the valve element,
• said first surface portion and said second surface portion of said valve element exposed to a pressure communicated by said inlet opening, whereby the valve element is hydraulically balanced, so as to be solely subject to the action of said solenoid and said elastic means,
• said valve element body slidably mounted directly within the cylindrical cavity of said valve body, without the use of sealing rings, and
• said first surface portion and second surface portion of said valve element body defining axially opposite ends of a circumferential groove bounded by said first surface portion, said second surface portion, and a connecting portion of a cylindrical outer surface of said valve element body connecting said first surface portion and said second surface portion, said groove comprising a recess in said valve element body recessed relative to an outermost surface of said valve element body in a direction radially inwardly relative to said cylindrical cavity of the valve body.