Device for operating a valve in an internal combustion engine
AssigneeCentro Ricerche Fiat Societa' Consortile Per Azioni
InventorsRenato Filippi, Francesco Vattaneo
Life of this patent
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Abstract
The portion of the profile of an asymmetric cam which controls the closure of a valve in an internal combustion engine is steep enough to ensure that, when the engine speed exceeds a threshold value, the valve closes, without contact between the valve and the cam , within a period of time which is substantially fixed as the engine speed varies, so that the angle of the cam upon closure increases with increases in the rate of rotation of the cam. The active surface of a bucket-type tappet interposed between the cam and the valve has a flat portion substantially perpendicular to the line of movement of the tappet and a curved portion which is connected to the flat portion and has a uniform radius of curvature so as to have a convex region facing the cam.
Claims8
A device for controlling a valve in an internal combustion engine, of the type including:
- a valve which is movable between a position in which a duct is closed and a position in which the duct is open,
- resilient means for biasing the valve towards its closure position,
- valve-operating means for cyclically controlling the movement of the valve towards its opening position against the action of the resilient means, the operating means including a rotary cam with an asymmetric profile including a first portion with an eccentric profile for controlling the movement of the valve towards its opening position and a second portion with an eccentric profile steeper than the eccentric profile of the first portion, for controlling the movement of the valve towards its closure position, and a tappet operatively interposed between the cam and the valve and having an active surface facing the cam, the active surface being engageable by the profile of the cam, at least during the movement of the valve towards its opening position so that, when the speed of rotation of the cam exceeds a threshold value, the active surface of the tappet loses contact with the profile of the cam and the closure movement of the valve is therefore unrelated to the rotation of the cam and is completed within a substantially fixed period of time, regardless of the speed of rotation of the cam, wherein the active surface of the tappet has a first, flat portion substantially perpendicular to the line of movement of the tappet and a second, curved portion which is connected to the first, flat portion and has a uniform radius of curvature, so as to have a convex region facing the cam.
Dependencies are inferred from the claim text.