Patent ID: 6530350
Filing Date: 2003-03-11
Classification: F01L

Abstract:
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 brings 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, in which at least one of said tappets controls the respective induction or exhaust valve against the action of said elastic return means via the interposition of hydraulic means including a hydraulic chamber (C) containing fluid under pressure; said hydraulic chamber containing fluid under pressure being connectable, via a solenoid valve, to an outlet channel for decoupling the valve from the respective tappet and causing fast closing of the valve against the action of respective elastic return means; 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 and the guide bushing, said variable-volume chamber being in communication with the hydraulic chamber (C) containing fluid under pressure by means of a communication port constituted by an end aperture of said guide bushing, said piston having an end appendage designed to be inserted into said end aperture during a final stretch of a closing stroke 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 a proximity of its closing, in which the aforesaid outlet channel communicates with an accumulator for fluid under pressure and with a feed pipe for feeding the fluid coming from a feed pump, wherein connected to the aforesaid outlet channel, upstream of the solenoid valve, is at least one supplementary fluid reservoir, bled off to the atmosphere, which is partially filled with fluid in the normal operating condition of the engine, is at least partially emptied following upon contraction of the fluid in cold conditions, and fills most following upon expansion of the fluid in hot conditions, both when the engine stops and when it is running, as the case may be.