SPHERE DIFFERENTIAL ON SEMI-ELLIPTICAL TRACKS AND TRANSLATORS COMBINED IN PAIRS

In the automotive sector there are prior art gear differentials defined by the group of planetary gears engaged with the group of satellite gears, the derived motion of which is transmitted to the wheels of a vehicle.

In addition to this system, which can be defined as traditional, there is also a new system defined in detail as a sphere differential on semi-elliptical tracks, the main elements of which are: two shafts (A) and (B) connected to the wheels in which no gears are applied but in them a series of semi-elliptical tracks are engraved on which one or more series of spheres are assembled.

The spheres are rotated by the intermediate elements called translators which are at the same time rotated by the longitudinal tracks made in the thickness of the container housing called the cylinder (C).

These types of differentials in the transmission of motion have a yield which must be classified as such that it does not exceed 50% of its actual potential.

This reality derives from the fact that, since the semi-elliptical tracks engraved in the shafts (A) and (B) are of two different types, that is to say, of the type (Z) and the type (R) and they extend, seen on a single line, with different inclinations from each other, it occurs that the translator, moving longitudinally gripping the spheres along the above-mentioned tracks of different inclination, must be assembled only with the spheres of equal inclination and the others left to another translator. This system results in the fact that for each completed semi-elliptical track, only two spheres are used, one every 180° instead of four, and naturally the space interposed from 90° to 180° and from 180° to 360° remains unused, in which two other spheres might be installed.

This fact represents the theory well illustrated in the description of the patent published with document EPO no. 202000015964 and also disclosed with document PCT/IT2021/050199.

This impossibility of rendering uniform the movement induced by the tracks (Z) and (R) on the same line has conditioned the use of the translators which are assembled around the circumferential circle of the shafts in such a way that the synchronism of movement in a direction is only achieved if two translators are positioned and assembled one at 180° from the other, since the semi-elliptical tracks are also constructed in such a way that they reverse the inclined direction every 180°, exactly as if it were necessary to fold a complete ellipse at the centre and create two semi-ellipses with equal inversion curves.

Since in the point of reversal of the inclination, referred to as zero point (0) we would have the correlation of the reversal of the longitudinal movement of only two translators located on the cylinder at 180°, the other two translators which complete the assembly circle, will in turn move in a synchronised fashion with each other but only on the tracks of the different type engraved in an alternating and progressive fashion in the shafts, so that there is a drawback in the use of the power which reaches a maximum of 50%. This is due to the impossibility of using the natural asynchronism due to the various inclinations of the semi-elliptical tracks of different types engraved in the shafts (A) and (B), inclinations which can be used on the longitudinal line of movement of the translators.

In order to overcome this drawback, these systems construct a greater number of semi-elliptical tracks of the type (Z) and the same number of type (R). However, this increase has a further drawback, that is to say, that the shafts (A) and (B) extend in length in a proportional manner, which results in higher production costs due to the use of a greater quantity of steel. In order to overcome these problems, a new differential has been studied, which is considered valid to obtain an industrial invention patent.

The field of application of the following invention is that of the innovative mechanics on differentials for motor vehicles defined by a particular and characteristic shape of the translators combined in pairs, that is to say, the technical problem dealt with is that of providing a pulling unit inside the differential which resolves the problem of the described asynchronism of the tracks (Z) compared with the inclination of the tracks (R) in a single line, in all the conditions and applications suggested by the sphere differential on semi-elliptical tracks, in which each translator simultaneously controls the spheres engaging both with the tracks (Z) and the spheres engaging with the tracks (R) guaranteeing the substantial improvement in the overall efficiency of the differential in all the conditions of use.

The advantage of the invention is obvious and is that of providing an actuation method which is able to pick up and use the other 50% of the pulling power suggested by the differential sphere system on semi-elliptical tracks with the pairs of translators reaching the use of 100% of the total potential. The other advantage to be obtained is that the extension in length of the differential in which the total use of 100% of its potential is obtained results in the reduction of 50% of its extension along the axis of rotation, thus also reducing the use of steel. These problems and relative solutions are described in more detail below and are resolved by the invention with the pulling and operating unit, made according to the following claims, wherein the features and advantages of the invention are described in detail below with reference to some embodiments, illustrated by way of example and without limiting the scope of the invention, with reference to the accompanying drawings, in which:

- Figure 1 is a double track line for the functional construction of the engraving performed on a numerically controlled lathe which represents the circumferential rotation of the centre of the sphere about the shafts (A) and (B);

- Figure 2 is a schematic view of the assembly of two opposite shafts (A) and (B) in which a traditional translator of the type (T) engages with a single type of semielliptical track of the type (R);

- Figure 3 shows the invention of the new translator with the concave recesses and the elongate circular arc recesses;

- Figure 4 shows mainly the translators (BT) which control both types of tracks (Z) and (R) both in a single pair and in a pair superposed in transparency with the shafts (A) and (B).

- Figures 5 - 6 - 7 show embodiments of the translators (BT) which control two tracks (Z) and two tracks (R) for each shaft. - Figure 8 shows a cutaway of the assembly of the old system wherein the translator (T) controls only two spheres of the type (Z) of which one of the two is not visible.

The aim of the invention relates to a mechanical differential, the operation of which is determined by the shape with which the translators which control the spheres are made. This shape differs completely from the translators known and used in all the sphere differentials for automobiles already published and known such as patent PCT/IT 2021/050199, EPO/IT 202000015964.

Any elliptic differential works according to the principle whereby the semi-elliptical or elliptical tracks (Z) and tracks (R) are engraved in the two shafts coming out of the differential box. The tracks (R) are identical to the tracks (Z) and adopt the name (R) since they are engraved alongside the tracks (Z) after having rotated the shaft by 45°, or 22.5°, or by 90°, or another gradation which determines the distinctive construction characteristic of the engraved shaft; for example: shaft (A) and shaft (B), the tracks are concave in shape if the spheres are to be used as pulling elements or they have a shape suitable for the use of cylinders as pulling elements. For this reason, in the following description the term sphere also comprises the cylinders.

The spheres are kept spaced in the semi-elliptical tracks from the translators which adopt the shape of the intermediate elements (spheres) (cylinders) but also the tangential shape of the concentric shafts below, but also of the winding cylinder which contains them.

The translator (BT) according to the invention substantially differentiates any sphere differential and the invented object allows non-existing mechanical features to be added to the differential and which cannot be obtained without the invention.

In short, each translator (BT) consists of a metal rod wherein on one of the longitudinal sides, that is, on the side for contact with the other translator, there are a series of deep and sized recesses such as to wrap and drive *4 of a sphere; on the same side and in an alternating fashion, another series of recesses is also formed with a profile which we define as an elongate circular arc, the length of which is predetermined and is equal to the selected construction step for engraving the semi- elliptical tracks in the shafts (A) and (B); the recesses with an elongate circular arc prevent the spheres driven by the other coupled twin translator from escaping from the sliding translation line.

The translator (BT) in the side towards the centre of rotation of the differential is in the form of an arc of a circle such as to copy the circumference of the shafts on which it is installed; this side is also called “concentric side C” whilst in the opposite side it may be an arc of a circle whose radius is less than the radius of construction of the shafts (A) and (B) or it adopts the shape of the octagonal track made in the thickness of the cylinder (C), so this side is formed by two straight lines which meet in a rounded edge shared by the two sides of the octagon.

It should be noted that in the description the spheres also adopt the name of spheres (Z) or spheres (R) on the basis of the respective tracks on which they are active.

For simplicity, Figure 3 shows only two concave recesses (AZ) and (BZ), but each translator (BT) may have other concave recesses and as many circular arc recesses (ACR) and (BCR), see Figure 3, as the semi-elliptical tracks engraved in the shafts (A) and (B). By coupling in the opposite direction two combined translators (BT) as in Figure 4, the assembly seen at the top resembles an entire translator of the old system since it occupies *4 of a circle inside the cylinder (C).

On the other hand, they are completely different also in terms of the function they perform: they are able to control the active work both of the spheres engaged with the winding recesses (AZ) and (BZ) of the translator (8) slidable in the tracks (Z) and of the counter- thru st tangential spheres active in the tracks (R), which move tangentially in the circular arc recesses (ACR) and (BCR); these latter spheres, however, are pulled by the twin translator (7) by means of its winding recesses. As shown in the drawing, each translator (BT) performs half the work with the winding recesses, whilst the other forming the pair performs the other half the work with its circular arc recesses.

This complementarity cannot be seen in Figure 2 wherein the entire translator (T) being forced to calibrate only the two spheres (S) between (A2R) and (B2Rs) must leave free the tracks (A1Z) and (B IZ) on which it is impossible to assemble other two spheres since they would move asynchronously on the same line of translation of (T).

In short, the spheres (AZ) and (BZ) can be carefully observed in Figure 4 which are in a position called a “dead centre” since they are not able to drive due to the lack of virtual intersection since the tracks are parallel to each other.

It should be noted that the term (Z) indicates zero, the dots (0) at the sides of the tracks also indicate the position of two other spheres which are not drawn so as not to complicate the drawing whilst the fourth sphere is not in view from the opposite side of (AZ) and (BZ).

For this reason, four spheres are assembled in the track (AZ) all in an idle position, that is, zero and equally in (BZ). In this position, the pair of combined translators (7) and (8) can pull only with the spheres slidable in the track (A2R) and (B2RS) of which a single sphere per track is drawn, the plus signs (AT) indicate the position of other spheres, and the other two are behind not in view.

In this case, the translator (7) with the concave recesses drives the spheres (A2R) and (B2Rs) and the elongate circular arc recesses keep the spheres (AZ) and (BZ) tangential to the translator (8).

In conclusion, it has been seen that two active spheres (A2R) with (B2Rs) share the same pulling line with other two spheres (AZ) with (BZ) which are idle, this assembly “two by two” exchanges the pulling position in a harmonic and progressive manner each quarter of a turn. The other pairs of translators also perform the same function in a synchronised fashion.

The principle follows that in the arc of rotation of 360° all four pairs of translators (BT) are always in the pulling phase and the zero point is never generated for each translator as was the case in the old system wherein always at each quarter of a turn two complete translators entered in total idleness and only the other two pulled with only two spheres per track.

The principle is essential as well as decisive and is explained in the fact that when in the old system the idle semi-elliptical tracks cancelled out two individual translators from the synchronism of the intersection for an instant, with the pair of translators (BT) the zero instant does not exist but is integrated by the other two spheres in full 90° intersection and the puling passes from two to four and overall each track intervenes in the circle of 360° with an engagement every 90° for a total of four spheres generating the duplication of the power.

In the container cylinder to the left of Figure 4 there is the position of eight translators (BT) numbered from 1 to 8 and it can be seen how they are coupled at the top; (1 and 2) which form a pair which uses the same track (PT) also called “NORTH CARDINAL TRACK” (PT): this defines better the concept of track in this cylinder (C).

In effect, observing the perspective of the cylinder (C) to the right of Figure 4 it can be seen that the inner shape is an octagon with rounded edges in which the NORTH track (PT) is understood as a side of the octagon drawn in a geographical NORTH position plus a half side of the octagon in a NORTH-EAST position plus another half side of the octagon in the NORTH-WEST position, wherein the pair (1 and 2) on the one side with the translator (BT) (1) works tangentially with the translator (BT) (8), and on the other side the translator (BT) (2) works tangentially with the translator (BT) (3).

Figure 4 shows the place and the logic of the couplings in a progressive fashion and also the freedom of movement which the translators (BT) adopt from each other which, respectively, move in the longitudinal line independently following the semielliptical tracks engraved in the shafts of the differential.

Figure 2 shows that the traditional translator of the old system (T) with its spheres cannot control simultaneously the tracks (Z) and the tracks (R) but only the tracks of one type, that is to say, if it controls the tracks (Z) it cannot control the tracks (R) due to the fact that the winding extension of different semi-elliptical tracks in the shafts (A and B) and controlled on the same guide line of the cylinder cannot be synchronised or compatible with a single movement of the entire translator of the old system (T). The drawing shows the engaged tracks better defined as tracks (A2R) and (B2R), the first acronym (A) for the shaft (A), (2) for the second track, (R) rotated, the second acronym (B) for the shaft B), (2) for the second track, (R) rotated and (S) mirrored. It is important to note that the translator of the old system is highlighted with the acronym (T). Figure 1 presents the guide lines for engraving the semi-elliptical tracks in the shafts (A) and (B), the movement of (R) ) upwards indicates the rotation of the shaft in the forming lathe, before starting the engraving of the tracks (R).

Figure 8 shows by way of comparison a cutaway view of the differential of the old system which uses individual translators with the acronym (T) which is not able to control different tracks, and which, therefore, uses only 50% of the useful potential in a differential with elliptical or semi-elliptical tracks.

Figure 5 shows the eight translators (BT): as may be seen, the translators (I and II) are forced to move longitudinally always on the basis of the spheres or cylinders, which follow the tracks which are not visible.

In this case there are multiple tracks and the translators drive several spheres (S). Figure 6 shows the cutaway of the cylinder (C) which contains the translators and the shafts (A) and (B).

Figure 7 shows an instant of the eight translators (BT) from 1 to 8 and the various synchronisations .

It may be said that the four pairs of translators (BT) always drive and synchronise four spheres for each track (Z) and four spheres for each track (R) engraved in the shafts (A) and in the shafts (B); any system of entire translators (T) see Figure 8 belonging to the old system, by comparison, only drive and synchronise two spheres for each track (Z) or only two spheres for each track (R).

Since this optimisation has been found, it is possible to use the combined translator (BT) to transport a greater power and simultaneously reduce in a calculated manner the diameter of the spheres or rollers, by way of confirmation it is possible to simply compare the moment of inertia of the assembly on a single track which uses two larger spheres, with respect to the moment of inertia on the assembly of four smaller spheres on a track of the same type.

This system of combined translators has been designed to allow a differential to be made which halves the extension in length of the cylinder (C) and of the shafts (A) and (B) of the long differential.

The extension in length of cylinder and shafts may be well used in the application on an electric motor for automotive transport, since it extends as a shaft and covers the entire length of the electric motor, replacing in any case the entire length of the motor- driven shaft, without generating any greater overall dimensions. But in the bridge differential which is normally used in trucks or automobiles, installed between the rear wheels, this length must be reduced as much as possible to reduce the use of steel and consequently considerable savings on the general costs under equal conditions of yield. For this reason, the reduction in length translates into the concentration of the spheres in half of the semi-elliptical tracks engraved on (A) and (B) whilst at the same time maintaining the power of transmission of the pair on a shorter cylinder. It is important to note that the pair of two translators (BT) is installed around the circumference of the shafts (A) and (B) and occupies the space of a single translator of the old type (T); so the eight translators (BT) are always in the same space as four of the old type (T). It should be noted that this attempt to concentrate four spheres on each track has been made differently so as to reach eight spheres, the diversity is achieved with some penalties in the old system.

And this result has led to a considerable increase in the external diameter of the cylinder, but not only, this attempt has caused the indispensable addition of two alternative elliptical tracks on the surfaces for contact with the centre of the shafts (A) and (B) and also the application of a new element, that is, of the cross (CR) interposed between the shafts, which controls the spheres vertically in such a way that the costs of the translators for applying the cross disc (CR) have doubled, also causing variations in engravings and even more evident increases for fixing the cross (CR) to the cylinder.

Other cases involved the use of up to eight individual translators each of which controls only two spheres, doubling the diameter of the circumference of the cylinder. These systems are clearly counterproductive because of the constructional complexity that is uncompetitive. It is also obvious that in these descriptions it can be noted that in these differentials what is improved in terms of length is lost by the increase in diameter and also due to constructional complications, which is the opposite of our aim “to achieve the minimum diameter” of the assembly.

It should now be noted that the pair of translators (BT) is used in the semi-elliptical track differential as characterised by the principle that the combined translators simultaneously control the spheres of any type with a constructional simplicity and a perfect functionality of application in the bridge differential for trucks and automobiles. With this, the aim of maximum efficiency, with a constructional economy and limited overall dimensions, is achieved in a definitive and optimum manner.

This optimisation transferred to the resistance of the materials is decisive since the choice of the materials for constructing a perfect product must take into account the lower production of sliding friction resulting from the use of anti-friction materials, which are perfectly suitable for resisting the forces determined by the thrusts of the spheres, distributing these concentrated forces from two to four contact points; the total pulling force is thus divided and always distributed on four points per track instead of two, halving the penetration effect between sphere and semi-elliptical track.

In short, the invention may be optimally used as a differential bridge since the container cylinder extends in length exactly less than half of the length of the same differential with entire translators of the old system.

A second example embodiment is the application in any electric motor since it is applied in the same position occupied by the drive shaft, so that the entire useful extension in length makes it possible to use in the shafts (A) and (B) a greater number of semi-elliptical tracks as much as they find space in this extension with consequent optimisation of the overall dimensions of the external diameter.

That is to say, if the designer can increase the number of spheres, they may at the same time proportionally reduce the relative diameter without losing the power transmitted with a consequent advantage of the motor-differential assembly which uses an enormous power in a predetermined space. For this installation a speed variator reduction gear unit will be applied at the sides, which will be obvious from the prior art which is not covered by this invention.

Summing up, this description highlights the advantage achieved with the creation of the translator (BT) which is obvious also from the description, that is to say, the new translator differential (BT) doubles the power transmitted whilst halving the expansion on the length in such a way as to also obtain the significant reduction in the use of steel and consequent reduction of the total cost of the invention whilst keeping unchanged the outer diameter of the invented object.

The above description amply describes the accompanying drawings in Figures 1 to 8.