Internal combustion engine with variably actuated valves

multi-cylinder internal combustion engine, comprising:

• at least one intake valve and at least one exhaust valve for each cylinder, each provided with respective spring means for biasing the valve to its closed position, in order to control respective intake conduits and exhaust conduits,
• a cam shaft for actuating the intake valves of the engine cylinders by means of respective tappets,
• wherein each of said tappets drives the respective intake valve against the action of said biasing spring means with the interposition of hydraulic means including a chamber of fluid under pressure,
• a solenoid valve for communicating said chamber of fluid under pressure to an outlet channel, in order to uncouple the tappet from the respective valve and cause the rapid closing of the latter under the action of the respective biasing spring means,
• electronic control means for said solenoid valve, in order to vary the opening timing and stroke of the intake valve as a function of at least one parameter of operation of the engine,
• characterized by the combination of the following features:
• the engine is of the type comprising at least two intake valves for each cylinder, which control respective intake conduits,
• the engine has a fuel injection feeding system and lacks of a throttle valve arranged upstream of the engine intake manifold, the air flow fed to the engine cylinders being controlled only by the intake valves of the cylinders,
• the two intake valves associated with each engine cylinder are provided with two respective solenoid valves for controlling communication of the respective pressure chambers to said outlet channel, so that the two intake valves can be actuated in different ways and independently from each other,
• said electronic control means are able to open a first intake valve of each cylinder of the engine only above a pre-determined running condition of the engine, the second intake valve being the only valve to control the air flow fed to the cylinder below said running condition,
• the two intake conduits associated with each cylinder have specific shapes which are different and such as to favour the mixing of the air flows coming from the two intake conduits within the combustion chamber,
• wherein the tappet associated with each intake valve is arranged with its axis substantially at 90.degree. with respect to the stem of the valve and in communication with the respective pressure chamber of said hydraulic means for pressurizing the fluid therein, and
• wherein a piston is slidably mounted in a cylinder disposed in axial alignment with said valve stem with one end of the piston in engagement with said valve stem and an opposite end of said piston in communication with said respective pressure chamber whereby upon movement of said tappet by said cam shaft, the fluid under pressure in said pressure chamber will cause movement of said valve to an open position.