Abstract:
An internal combustion engine is equipped with a variable actuation system for the intake valves (7) including a chamber of fluid under pressure (C) interposed between the intake valve (7) and the respective controlling cam, and a solenoid valve (24) whose opening causes the pressure chamber (C) to discharge such as to determine the rapid closure of the valve (7) by effect of the respective biasing spring means (9), even when the respective cam would tend to keep the valve open. The variable valve operation system is used in combination with the use of cams controlling the intake valves shaped in such a manner as to give rise to an intake valve lift profile including a boot portion (C2) at substantially constant lift. Such boot portion is provided in the initial part of the intake valve opening cycle, in advance with regard to the TDC, in the case of a supercharged direct-injection petrol engine. In the case of a diesel engine, on the contrary, the boot portion (C2) is provided in the final part of the intake valve opening cycle, after the BDC.
Abstract:
PROBLEM TO BE SOLVED: To provide an internal combustion engine with a variable actuation system of an intake valve provided with an improved solenoid valve, and the solenoid valve for the engine.SOLUTION: A valve element 105 has a cylindrical body having a first conical surface part C1 and a second conical surface part C2 on the surface of the cylindrical body. The conical surface parts have conical shapes opposite to each other, both exposed to the pressure transmitted from inlet openings 102 of the valve, and by that, the valve element 105 is hydraulically balanced. The first conical surface part C1 and second conical surface part C2 are defined by the axially opposite ends of a circumferential groove N formed on the cylindrical outer surface of the body of the valve element 105. The first conical surface part C1 constitutes a part of the valve element 105 which cooperates with a valve seat 104. The second conical surface part C2 has an outer diameter substantially identical to the diameter of the annular edge defining the valve seat 104.
Abstract:
PROBLEM TO BE SOLVED: To prevent reduction in a swirl ratio occurring at the end of a compression stage, in a combustion chamber for a diesel engine, which arranges engine valves along an axis inclined with respect to a cylinder axis by an angle greater than 8°.SOLUTION: A bottom surface H1 of a cylinder head includes a flat surface CO1 delimiting a combustion chamber, perpendicular to a cylinder axis and spaced from the bottom surface H1 of the cylinder head H, and the flat surface CO1 is a circular surface concentric with the cylinder which is joined to a plane of the bottom surface H1 of the cylinder head H through a substantially conical annular surface CO2, with a dome-like rounded or arched profile.