To internal combustion engines with variable valve actuation

Claim 1

Internal combustion engine, comprising: at least one intake valve and at least one exhaust valve for each cylinder, each provided with respective spring means returning the valve to its closed position, for controlling the communication between the respective intake and exhaust conduits and the cylinder, a camshaft, for actuating the intake and exhaust valves of the engine cylinders by means of respective tappets, each intake valve and each exhaust valve being driven by a cam of said camshaft, wherein at least one of said tappets is adapted to drive the respective intake or exhaust valve, against the action of said return spring means, with the interposition of hydraulic means including a chamber of fluid under pressure, said chamber of fluid under pressure being adapted to be connected by means of a solenoid valve to an outlet channel, for uncoupling the valve from the respective tappet thus causing the quick closing of the valve under the action of the respective return spring means, electronic control means for each solenoid valve, for varying timing and opening travel of the respective valve as a function of one or more parameters of operation of the engine, and a pressure accumulator communicating with said pressure chamber, wherein said engine comprises an auxiliary accumulator including: a rigid casing, a piston movable within the rigid casing and defining a variable volume chamber connected to a line for supplying fluid under pressure to the outlet channels associated with the various cylinders, spring means interposed between the piston and an end wall of the rigid casing and tending to push said piston towards a position at which the volume of said variable volume chamber is minimum, pawl-like stop means defining a number of subsequent stop positions for said piston, at which the piston is held, as long as it is displaced against the action of said spring means due to the increase of pressure within the variable volume chamber, and means for deactivating said stop means when the engine is started, so as to cause the piston to rapidly return to its rest position, under the action of said spring means.