D The present invention concerns a fluid-mechanical system that allows a variation in advance or in delay of the o- pening and/or the closing of each valve of an internal or non-internal combustion engine.

10 Many systems are already known in the art for obtaining a variable phasing of internal or non-internal combu¬ stion engine valves.

The an comprises mechanical systems and systems working lϊ with fluid under pressure; in both cases the realization solutions are often rather complex and do not consider the possibility of elastically deforming the structure of the cam or parts of the same.

20 The main principle on which is based the device accord¬ ing to the present invention consists of the possibili¬ ty, making use of fluid under pressure, of deforming the cam or parts of the same so as to obtain a shape being variable keeping the continuity of functioning of the

2. engine's revolutions and of the engine's couple; by va¬ rying che shape it is possible to modify the opening and closing moment of the suction and discharge valves. The deformation caused by the fluid under pressure elasti-

cally concerns the cam in its whole or appropriate ela¬ stic elements placed in co-action with the shape of the cam or with parts of the same; in the first case the va¬ riation of the shape takes place, in a more or less con- siderible entity, on the whole structure of the cam, whi¬ le in the second case it concerns mainly the active parts of the cam, i.e. the opening and closing part or only parts of the same.

Figures 1, 2, 3 and •. show some preferred embodiments, in a scheme, of realization solutions concerning the de¬ vice according to the present invention; each figure shows the section of the cam performed in a perpendicu¬ lar plane to the rotation axis.

Figure 1 shows a hole 1 with the fluid under pressure; appropriate small holes 2 allow the fluid to fill up ca¬ vities 3. The geometry of the cavities is studied in such .-. way as to realize a total structure of the cam having a differential resistance; the fluid under pres¬ sure, pressing onto the walls of cavities 3, causes a deformation of the soft walls 4 (a prevaling deformation with respect to the one of the remaining part of the structure) and therefore a variation of the cam's shape, thus determining a phasing modification of the valve.

The modification of the shape increases according to the

increasing internal pressure of the fluid; it is obvious that if for each of the two cavities pressure surfaces different in extension are realized, with the same pres¬ sure also different deformations of the opening and of 5 the closing parts are obtained. The same result is ob¬ tained with different pressures with the same or less surfaces .

In figure 2, the soft structure of the cam consists of a 10 "jacket" 4 adhering to the internal structure of said cam; a.so in this case the fluid under pressure acting directly and/or through small pistons onto the internal surface of the jacket in correspondence to cavity 3 cau¬ ses a deformation of said jacket, prevailing with re- 1. spect to the deformation of the remaining structure, and therefore the variation of the cam's shape; for realiza¬ tion reasons the jacket is built with a constant or va¬ riable section.

20 In figure 3, the soft structure of the cam consists of a jacket 4 whose deformation is prevailing with respect to the om of the remaining structure, connected to struc¬ ture 5. having a circular directive, through a common connection element 7 (a small key, a small tongue, a

25 grooved shape, etc.); this all may be obtained using, for the structure 5, an also non-circular directive; in the mentioned figure the fluid under pressure acts onto small pistons' 6 that press the internal surfaces of ja¬ cket 4.

Relating now to the possible variants shown in figures 2 and 3, the jacket 4 may be realized in different manners according to the deformation degree requested. For in¬ creasing the deformability said jacket has axial or bent 5 cuts or it is replaced, partially or totally, by an ela¬ stic element repeatedly wound around the cam's shape.

In figure 4, the soft structure consists of elements 4' hinged in points E and F; along the sides opposite to

10 said pcints, the elements 4' are in co-action with the structure 5 through elastic elements , internal or ex¬ ternal to said cam, that may be deformed. In this case the fluid, pressing onto the walls of cavity 3, makes rotates the elements 4' aroung the fulcrums E and F;

1. said elements, elastically deforming elements K, whose deformation is prevailing with respect to the one of the remaining structure of the cam, do gradually move up to the extreme position shown in dotted line. For exempli¬ fying purposes and in the non-limiting condition in ( which the play between cam and element moved by the same is different from zero, dotted line 9 shows the geome¬ trical place circumference of the points of starting o- pening and ending closing of the valve; B and C show the cutting points between said circumference and the exter- 1 nal shape of elements 4' when said elements are in rest¬ ing position. When inte pressure increases said points gradually move to the extreme position shown in points A and D (maximum pressure of the fluid); therefore, acting on the pressure value, the opening as well as the clos- 0 ing of the valve may be advanced or delayed.

The fulcrums E and F, provided in number of two or more, may have any position (on top, lateral, at the centre, on bottom, intermediate). Elements 4', that are provided in numer of two or more, may occupy the whole extension of the cam or only one part of the same.

Furthermore, the phasing variation of the valves, beyond in the already described manner, may be obtained, always using fluid under pressure, moving the geometrical axis of the cam's base cylinder with respect to the rotation axis of the camshaft; the entity of the phasing varia¬ tion depends on the entity of said axis' moving. What a- bove described implies the presence of one or more free¬ dom decrees between the cam and the rotation shaft, that may be however controlled through the fluid under pres¬ sure .