Internal-combustion engine with hydraulic system for variable operation of the engine valves

An internal-combustion engine comprising:

• at least one induction valve and at least one exhaust valve for each cylinder, each valve being provided with respective elastic means that bring back the valve into the closed position to control communication between the respective induction and exhaust ducts and the combustion chamber;
• a camshaft for operating the induction and exhaust valves of the cylinders of the engine by means of respective tappets, each induction valve and each exhaust valve being actuated by a cam of said camshaft;
• wherein at least one of said tappets control a respective valve against the action of said elastic return means by interposition of hydraulic means including a hydraulic chamber containing fluid under pressure;
• said hydraulic chamber containing fluid under pressure being connectable, to an outlet channel for decoupling the valve from the respective tappet and causing fast closing of the valve under the action of respective elastic return means;
• a solenoid valve operatively associated with said outlet channel to open and close said outlet channel;
• said hydraulic means further comprising a piston associated to the stem of the valve and slidably mounted in a guide bushing, said piston being set facing a variable-volume chamber defined by the piston inside the guide bushing, said variable-volume chamber being in communication with the hydraulic chamber containing fluid under pressure by means of an end aperture of said guide bushing, said piston having an end appendage designed to be inserted into said end of the valve in order to restrict the communication port between said variable-volume chamber and said hydraulic chamber containing fluid under pressure, so as to slow down the stroke of the valve in the proximity of its closing,
• wherein the aforesaid piston for actuating the valve stem has its axis aligned with the axis of the respective tappet, and wherein said tappet is slidably mounted in a tubular element which constitutes an integral prolongation of the guide bushing for guiding the piston for actuating the valve stem.