- The drawings make it clear that in both forms of realisation shown, the movement is transmitted by the driving shaft to the driven shaft through a couple of elements with a curve coupling surface so as to obtain a variation of the transmission ratio as smooth and as wide as possible. Such elements remain always engaged since they move simultaneously along their respective incident axes of rotation varying at any instant the radii of the contact circumferences and, as a result, the transmission ratio which can assume an almost infinite range off values. Due to the simultaneous translation of two parts, when the contact point of one of them reaches and passes beyond the point lying along the rotation axis and having an almost nil speed, the driven element starts rotating in the direction opposite to the previous one as it occurs in traditional gearboxes when the reverse speed is engaged.
In the realisation form shown in FIG. 1, the driving element 1, rotating and moving along the Y axis, shows an almost hemispherical conformation in the end to couple to the almost spherical end of the driven element 2, having a roto-translational movement along the X axis. Such element 1 forms a single body with the hollow shaft 3 which, through a splined coupling, receives the rotational motion by the driving shaft 4 on which it can slide lengthways moved by a hydraulic or oil-dynamic actuator with electronic control and connected to it by bracket 5. Such bracket is fixed to the hollow shaft 3 by two thrust bearings 6 and two roller cages 7, positioned to the two sides of the bracket to isolate it from the rotation imparted to the hollow shaft 3 by the driving shaft 4.
Similarly, the driven element 2 forms a single body with the hollow shaft 8 which, through a splined coupling, transmits the rotational movement to the driven shaft 9 on which it slides lengthways moved by a special actuator and by means of the bracket 5. Such bracket is fixed to the hollow shaft 8 by two thrust bearings 6 and two roller cages 7, positioned to the two sides of the bracket to isolate it from the rotation imparted to the hollow shaft 8.
The realisation form of FIG. 2, specially recommended in case of integral traction, foresees that the driven shaft 16 protrudes out of the gearbox with two aligned and opposite outputs. The main difference between the two realisation forms consists in the concave coupling surface of the driving element 10 having a maximum truncate conical conformation widening to the ends. Such element, having a roto-translational motion along the Y axis, remains always engaged with the driven element 11, having an almost spherical and roto-translating shape along the X axis, solidly fixed to the hollow shaft 12 which, through a splined coupling, receives the rotationaal motion from the driving shaft 13 on which it can slide lengthways moved by actuator 14, of hydraulic or oil-dynamic type and with electronic control, through the bracket 5, rigidly connected to 12 by the thrust bearings 6 and by the two roller cages 7, located to the two sides of the bracket to isolate it from the rotation imparted to the hollow shaft 12 by the driving shaft 13.
Similarly, element 11 is solidly fixed to the hollow shaft 15 which, through a splined coupling, transmits the rotational motion to the driven shaft 16 which can be connected to the two axle shafts of a transmission thanks to its double output from the gearbox. The hollow shaft 15 slides lengthways on 16 moved by actuator 14 through the bracket 5, rigidly fixed to 15 by the thrust bearings 6 and the two roller cages 7, positioned to the two sides of the bracket to isolate it from the rotation of the hollow shaft 15.
In the chambers 19 and 20 of FIG.1 where the shafts present are in a oil bath, despite the combined movements of rotation and linear translation of the hollow shafts 3 and 8, each one off them supported by a bearing 25 with internal helical slot, special gaskets 24 of a known type prevent oil from passing from such chambers 19 and 20 to chamber 17 where the transmission gears 1 and 2 with dry-friction clutch are positioned. Similarly, also in chambers 21, 22 and 23 of FIG. 2, where the shafts are in a oil bath and supported each of them by a bearing 25 with internal helical slot, suitable gaskets 24 of a known type prevent oil from passing from chambers 21, 22 and 23 to chamber 18 where the friction transmission elements 10 and 11 are located.
Possible variations to the represented and described versions could consist in the replacement of the hydraulic or oil-dynamic actuators with electromechanical devices or equivalent, suitable for the necessary linear translations.
The analysis of both realisation forms examined makes it clear that the engine brake which can be obtained with the use of such motion transmission elements is more rapid than the one which can be obtained with the present CTV gearboxes thanks to the velocity and smoothness with which such elements slide one onto the other.
Another characteristic of this variator deserving a mention is the possibility to be used as a replacement of the clutch since the simple linear transmission of pull-apart of one of the two transmission organs from the other allows to stop a vehicle or the spindle of a machine tool while keeping the motor run.
Also the proposed invention is especially useful in electrical vehicles since their autonomy, usually quite limited, would be improved by an almost constant rpm despite the speed variation.
Since the principle on which the motion transmission in the continuous variator is based is friction, the transmission elements should be coated with special ceramic films which guarantee the necessary friction. The recent evolution of the production of ceramic coatings brought important modifications to the process technologies enabling to lay ceramic films with very high mechanical and physical characteristics. Also, the involvement of techno-ceramic sector in the development of coatings more suitable for the invented continuous variator can lead to a cost reduction of the production of the variator itself which, due to low number of pieces of which it consists and their simplicity, is certainly more economic than the traditional automatic gearbox, CTV or equivalent.
Finally, notwithstanding the general characteristics of the illustrated and described versions, modifications or variations to the same, in any case included in the patent field, cannot be excluded a priori.
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