Abstract: A phase variator including a piston actuator slidable between two travel limit positions as a result of the supply of a flow of pressurized fluid to at least one chamber of the variator. Valves are provided in the variator for choking the flow associated with the at least one chamber so as to avoid axial end contact of the piston and casing and axial end contact of the piston and hub.

Abstract: In a mechanical device for changing the phase relationship between the engine shaft and a camshaft of an internal combustion engine, in which the phase change is achieved by a change in the angular position of a body kinematically connected to the engine shaft relative to that of a shaft kinematically connected to the camshaft by the movement of a piston and of an auxiliary annular element which are spaced apart axially and are interposed between the body and the shaft to which they are coupled by intermeshing teeth, a stop is provided for limiting the axial travel of the auxiliary annular element, advantageously stopping the piston owing to engagement in the teeth of the shaft and of the body.

Abstract: The single-acting phase variator includes a piston actuator movable towards an actuate position, as a result of the admission of a pressurized fluid to a supply chamber through a distribution and discharge duct opening in the chamber against the force of a spring. A valve is provided in the variator for connecting the distribution and discharge duct alternatively to a feed duct for the pressurized fluid or to a discharge opening for the rapid discharge of the fluid from the chamber.

Abstract: A timing variator disposed between a crankshaft and a camshaft of an internal combustion engine includes a body portion connected to the crankshaft and a hub connected to the camshaft. A piston is interposed between the body and the hub and coupled thereto by helical gearing for changing the angular position of the body relative to the hub. A torsion member is connected between the body and the hub for producing a torque therebetween and/or a braking device is disposed between the body and the hub to brake relative movement therebetween.

Abstract: A timing variator which is constructed to provide at least three predetermined different relative angular settings of the camshaft and the timing system of an internal combustion engine; the variator comprises a piston actuator slidable inside a space against a spring as a pressurized fluid is delivered into a supply chamber thereof. When the piston is to be stopped at a position intermediate to two end-of-stroke positions, in order to obtain an intermediate timing setting, pressurized fluid is delivered behind the piston, thereby producing an additional thrust concurrent with the spring thrust and partly balancing out the pressure of the medium being delivered into the supply chamber.

Abstract: The solution described enables the provision of a timing variator with internal circulation of the working servo-medium, while ensuring firm retention and centering ability relatively to the driving shaft (A).