Internal combustion engine with intake valves having a variable actuation and a lift profile including a constant lift boot portion

摘要

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.