Patent Description:
The differential is a power transmission member available in vehicles to distribute the torque coming from an input shaft to a pair of output shafts connected to respective wheels. In particular, as it is known, the differential allows different velocities to be delivered to the wheels, so as to allow each one of them to follow the relative trajectory during paths covering a bend or paths with different grips.

In its simplest configuration, a differential comprises a carrier, to which two shafts are constrained, and two satellites, which are placed on the shafts and mesh with two driven planetary gears, which are integral to the axle shafts, each connected to the respective wheel.

Known differentials are also provided with a locking function, which is configured to cause the two axle shafts to be integral to one another. This function is useful in case of a surface allowing for a reduced grip of the tyres, in which case one of the two wheels, if it were not constrained to the other one, would tend to skid, thus dispersing the torque.

Examples of known differential systems are disclosed in <CIT>, <CIT>, <CIT>, <CIT> or <CIT>.

However, known differentials are subjected to a constant need for improvements, so as to ensure a versatile use thereof and increase the functions thereof.

Therefore, existing vehicle differentials need to be improved.

The object of the invention is to fulfil the needs discussed above in an economic fashion.

The aforesaid object is reached by a differential group comprising the combination of features of claim <NUM>, the dependent claims show further advantageous embodiments of the invention.

The invention will be best understood upon perusal of the following detailed description of a preferred embodiment, which is provided by way of non-limiting example, with reference to the accompanying drawings, wherein:.

In the accompanying figures, number <NUM> indicates a differential group <NUM> according to the invention housed inside a casing <NUM> configured to delimit an inner space <NUM> suited for the purpose. The casing <NUM> further is advantageously configured to house part of the axle shafts <NUM>, <NUM> of an axle <NUM>, as shown in <FIG>, <FIG> or <FIG>. To this aim, the casing <NUM> can be manufactured as one single piece or in different parts depending on the assembling needs of the differential group <NUM> and of the axle <NUM>.

The differential group <NUM> is operatively interposed between the axle shafts <NUM>, <NUM> and a drive source <NUM>, such as a transmission shaft configured to convey the torque of an internal combustion engine or an electric motor, which is configured to transmit a torque to the axle shafts <NUM>, <NUM>.

The axle shafts <NUM>, <NUM>, as it is known, are advantageously concentric to one another around a common longitudinal axis A, cooperate - with a respective inner end 4a, 5a - with the differential group <NUM> and define a wheel hub at outer ends 4b, 5b of theirs.

The differential group <NUM> comprises a differential <NUM> and a transmission <NUM>, the differential <NUM> being operatively interposed between the axle shafts <NUM>, <NUM> and the transmission <NUM> and the latter being operatively interposed between the differential <NUM> and the drive source <NUM>.

The differential <NUM> is of a known type and comprises a carrier <NUM>, which carries a plurality of satellites <NUM>, for example four satellites, which are angularly equally spaced apart from one another by <NUM>° and are supported by a cross-shaped support <NUM>, which is rigidly carried by the carrier <NUM> and around whose arms the satellites <NUM> can rotate. In particular, the satellites rotate on the support <NUM> around axes contained in a plane, which is perpendicular to the axis A.

The satellites <NUM> cooperate with a planetary comprising a left bevel gear 15a and a right bevel gear 16b, respectively, which are rigidly carried by the axle shaft <NUM> and by the axle shaft <NUM>, respectively, on the respective inner portion.

The transmission <NUM> basically comprises a rotating structure <NUM> and a planetary gear <NUM>, which are operatively interposed between the drive source <NUM> and the carrier <NUM>.

In particular, the rotating structure <NUM> is configured to define a closed space <NUM> suited to house the planetary <NUM> and the differential <NUM>.

According to the embodiment shown in <FIG> and <FIG>, the rotating structure <NUM> is coaxial to the axis A of the axle shafts <NUM>, <NUM> and defines a first and a second opening 16a, 16b, which are configured to allow the inner ends 4a, 5a of the axle shafts <NUM>, <NUM> to be inserted inside it.

The rotating structure <NUM> is supported in a rotary manner by the casing <NUM> by means of rotary supports <NUM>, such as for example ball bearings. The rotating structure <NUM> is operatively connected to the drive source <NUM> by means of a toothed gear <NUM>, which is rigidly carried by the rotating structure <NUM> and is configured to cooperate with the drive source <NUM> so as to allow a torque to be transmitted. In particular, in the embodiment described herein, the toothed gear <NUM> is a bevel gear configured to mesh with a respective bevel gear <NUM> carried by a shaft <NUM> rotating around an axis B, which is perpendicular to the axis A of the axle shafts <NUM>, <NUM>.

Preferably, the rotating structure <NUM> is manufactured in different portions, in particular a first portion <NUM>' defining the first opening 16a and a second portion <NUM>" defining the second opening 16b. The two portions <NUM>', <NUM>'' advantageously are rigidly connected to one another, for example through threaded means.

Preferably, the toothed gear <NUM> is manufactured as a separate piece relative to said portions <NUM>', <NUM>" and is rigidly connected to them. Advantageously, the toothed gear <NUM> is connected, in a clamped manner, between the two portions <NUM>', <NUM>'' and is fixed to them through the same threaded means connecting them.

The planetary <NUM> comprises a plurality of satellites <NUM>, which are connected to the carrier <NUM> of the differential <NUM>, a solar <NUM>, which is housed around one of the axle shafts <NUM>, <NUM>, in the figures the left axle shaft <NUM>, and a crown <NUM>, which is rigidly carried by the rotating structure <NUM>.

In particular, the satellites <NUM> are free to rotate around a pin <NUM> rigidly carried by the carrier <NUM>, for example through threaded means, and, hence, cooperate with a toothing <NUM> defined by the crown <NUM> and with a toothing <NUM> defined by the solar <NUM>. In particular, the pins <NUM> are arranged in an oblique manner relative to the axes A, B described above, advantageously inclined to define an acute angle α facing the differential <NUM>.

The crown <NUM> is advantageously manufactured as one single piece together with the rotating structure <NUM> and, advantageously, is manufactured as one single piece together with the first portion <NUM>', in particular it is defined by an axial projection inside the space <NUM>, more preferably close to the opening 16a.

The solar <NUM> comprises a sleeve <NUM>, which is housed around the axle shaft <NUM> and is free to move relative to the latter both in a rotary and in a sliding manner, and a return <NUM>, which is coupled, in its rotation, to the sleeve <NUM> in an end portion of its.

In particular, the return <NUM> and the sleeve <NUM> are coupled to one another in a rotary manner, but are free from a sliding point of view, so that the sleeve <NUM> can move along the axis A relative to the return <NUM>. More in detail, the return <NUM> and the sleeve <NUM> are coupled by means of a grooved coupling <NUM> obtained by means of a toothing <NUM> extending in a radial direction from the inside of the return <NUM> and a toothing <NUM> extending in a radial direction on the outside of the sleeve <NUM> in an end portion thereof.

The sleeve <NUM> further defines a further shape coupling, which can selectively be engaged with the rotating structure <NUM>. In particular, it defines a further toothing <NUM> radially extending from its outer surface and arranged in an intermediate position between the two end portions of the sleeve as well as configured to selectively cooperate, in contact, with a toothing <NUM> carried by the casing <NUM>. In particular, the toothing <NUM> radially extends from the casing <NUM> towards the axle shaft <NUM>.

The sleeve <NUM> further defines a further shape coupling, which can selectively be engaged with the pins <NUM> supporting the satellites <NUM>. In particular, it defines a toothing <NUM>, which is obtained on an inner portion of the pins <NUM> facing the sleeve <NUM>. In particular, the toothing <NUM> defining the grooved coupling <NUM> is sized so as to be able to selectively - and depending on the position of the sleeve <NUM> along the axis A - mesh with the toothing <NUM>.

Consequently to the embodiment described above, the sleeve <NUM> is configured to move along the axis A so as to assume a first configuration (<FIG>), in which the toothing <NUM> meshes with the sole toothing <NUM> of the coupling <NUM> and, at the same time, the toothing <NUM> meshes with the toothing <NUM>, thus making the solar <NUM> integral to the casing <NUM>. The sleeve <NUM> further defines a second configuration (<FIG>), in which the toothing <NUM> meshes with the toothings <NUM> of the coupling <NUM> and <NUM> of the pins <NUM> and, at the same time, the toothing <NUM> does not mesh with the respective toothing <NUM>.

The differential group <NUM> comprises actuator means <NUM>, which are configured to allow the positioning of the sleeve <NUM> along the two positions mentioned above to be controlled.

In particular, the actuator means <NUM> are pneumatic actuator means and comprise a chamber <NUM>, in which a piston <NUM> is free to slide in a sealing manner. The chamber <NUM> is fluidically connected to a source of air under pressure, so as to be selectively filled with or emptied from said air under pressure. The piston <NUM> is held in a rest position by elastic means <NUM>, which are configured to exert, upon the piston, a force that is contrary to the one exerted by the pressure in the chamber <NUM> upon the piston <NUM> itself.

The latter, hence, can slide in a sealing manner in the chamber <NUM> depending on the force balance between the thrust provided by the elastic means <NUM> and the pressure of the air in the chamber <NUM> exerted on it.

The piston is further connected to the sleeve <NUM> so that, when there is no air inside the chamber <NUM>, it holds the sleeve <NUM> in the position of <FIG>, namely a position in which the rotating structure <NUM> and the solar <NUM> are free to rotate relative to one another, whereas, when there is air under pressure in the chamber <NUM>, the thrust provided by the elastic means <NUM> acting upon the piston <NUM> is overcome, thus causing the latter to move, moving the sleeve <NUM> to the position of <FIG>, namely a position in which the rotating structure <NUM> and the solar <NUM> are coupled to one another in a rotary manner.

The way in which the embodiment of the differential group <NUM> described above operates is the following one and it will be described using <FIG>, which show the lines followed by the torque from the drive source <NUM> to the differential <NUM>.

In the condition of <FIG>, the actuator means <NUM> are controlled so as to allow air to flow into the chamber <NUM>. In this way, the force acting upon the piston <NUM> overcomes the retaining force of the elastic means <NUM> and pushes the sleeve <NUM> so that it places itself in the operating condition in which the toothing <NUM> meshes with the sole toothing <NUM> and, at the same time, the toothing <NUM> meshes with the toothing <NUM>. In this condition, the torque coming from the drive source <NUM> is transmitted from the gearing consisting of the toothed gears <NUM>, <NUM> to the rotating structure <NUM>, in order to then reach the satellites <NUM>, which rotate between the toothing <NUM> of the return <NUM>, fixed relative to the casing <NUM>, and the toothing <NUM> of the crown <NUM> and transmit said torque to the carrier <NUM>, to which they are rigidly connected. The latter splits the torque between the axle shafts <NUM>, <NUM> in a known manner.

In the condition of <FIG>, the actuator means <NUM> are controlled so as to allow air to flow out of the chamber <NUM> (if present) or are at rest. In this way, the retaining force of the elastic means <NUM> holds the sleeve <NUM> in the operating condition in which the toothing <NUM> meshes both with the toothing <NUM> and with the toothing <NUM> and, at the same time, the toothing <NUM> does not mesh with the toothing <NUM>. In this condition, the torque coming from the drive source <NUM> is transmitted from the gearing consisting of the toothed gears <NUM>, <NUM> to the rotating structure <NUM> and, at the same time, to the satellites <NUM> and to the return <NUM>, which are all connected together to the rotation. Hence, the satellites <NUM> directly cause the rotation of the carrier <NUM> at the rotation velocity of the casing <NUM>. The latter splits the torque between the axle shafts <NUM>, <NUM> in a known manner.

Clearly, in the condition of <FIG>, the torque is transmitted according to a different gear ratio compared to condition 4B.

According to the first example embodiment, not according to the present invention shown in <FIG> and <FIG>, the rotating structure <NUM> is coaxial to the axis A of the axle shafts <NUM>, <NUM> and defines a first and a second opening 16a, 16b, which are configured to allow the inner ends 4a, 5a of the axle shafts <NUM>, <NUM> to be inserted inside it.

The rotating structure <NUM> is operatively connected to the drive source <NUM> by means of a toothed gear <NUM>, which is rigidly carried by the rotating structure <NUM> and is configured to cooperate with the drive source <NUM> so as to allow a torque to be transmitted. In particular, in the embodiment described herein, the toothed gear <NUM> is a bevel gear configured to mesh with a respective bevel gear <NUM> carried by a shaft <NUM> rotating around an axis B, which is perpendicular to the axis A of the axle shafts <NUM>, <NUM>.

Preferably, the rotating structure <NUM> is manufactured in different portions, in particular a first portion <NUM>' defining the first opening 16a and a second portion <NUM>'' defining the second opening 16b. The two portions <NUM>', <NUM>'' advantageously are rigidly connected to one another, for example through threaded means.

In particular, the satellites <NUM> are free to rotate around a pin <NUM> rigidly carried by the carrier <NUM> and, hence, cooperate with a toothing <NUM> defined by the crown <NUM> and with a toothing <NUM> defined by the solar <NUM>. In particular, the pins <NUM> are arranged in an oblique manner relative to the axes A, B described above, advantageously inclined to define an acute angle α facing the opposite side relative to the differential <NUM>.

The crown <NUM> is advantageously manufactured as one single piece together with the toothed gear <NUM>, in particular is defined on the opposite side relative to the toothing cooperating with the toothed gear <NUM>.

The solar <NUM> advantageously comprises a sleeve <NUM>, which is housed around the axle shaft <NUM> and is free to move in a rotary manner relative to the latter.

The sleeve <NUM> defines a toothing <NUM> radially extending from an end portion of the sleeve <NUM> extending towards the differential <NUM> and configured to mesh with the satellites <NUM>. Advantageously, given the inclination of the satellites <NUM>, said toothing <NUM> is a bevel toothing.

The sleeve <NUM> also defines a further toothing <NUM> preferably extending on the remaining portion of the sleeve <NUM>.

The differential group <NUM> further comprises a selector <NUM>, which is configured to selectively connect the sleeve <NUM> to the casing <NUM> or to the rotating structure <NUM>. In particular, the selector <NUM> basically comprises a cylindrical annular element defining an inner toothing <NUM> facing the sleeve <NUM> and an outer toothing <NUM> facing the rotating structure <NUM>.

The inner toothing <NUM> is configured to constantly mesh with the toothing <NUM> and slide along the axis A relative to the sleeve <NUM>, whereas the outer toothing <NUM> is sized so as to selectively mesh with a respective toothing <NUM>, which is rigidly connected to the casing <NUM>, or with a respective toothing <NUM>, which is rigidly connected to the rotating structure <NUM>.

In particular, in the case shown herein, the portion of casing <NUM> shown is very small, for clarity reasons, whereas the toothing <NUM> is obtained in the first portion of the rotating structure <NUM>', in particular in the area of the first opening 16a.

Consequently to the embodiment described above, the selector <NUM> is configured to move along the axis A so as to assume a first configuration (<FIG>), in which the toothing <NUM> meshes with the toothing <NUM> of the casing <NUM>, thus making the solar <NUM> integral to the latter. The selector <NUM> further defines a second configuration (<FIG>), in which the toothing <NUM> meshes with the toothing <NUM>; in this way, the solar <NUM> becomes integral to the rotating structure <NUM>.

In particular, the actuator means <NUM> are hydraulic actuator means and comprise a hydraulic cylinder <NUM>, for example a double-acting cylinder, which is configured to move a rod <NUM>, which is connected to the selector <NUM> and is configured to move it between the aforesaid first and second positions.

In the condition of <FIG>, the actuator means <NUM> are controlled so as to move the rod <NUM> in such a way that the selector <NUM> places itself in the operating condition in which the toothing <NUM> meshes with the toothing <NUM>, thus causing the sleeve <NUM> to be coupled to the casing <NUM>. In this condition, the torque coming from the drive source <NUM> is transmitted from the gearing consisting of the toothed gears <NUM>, <NUM> to the rotating structure <NUM> and to the satellites <NUM>. They rotate between the toothing <NUM> of the sleeve <NUM>, which is fixed to the casing <NUM> and to the toothing <NUM> of the crown <NUM>, and transmit said torque to the carrier <NUM>, to which they are rigidly connected. The latter splits the torque between the axle shafts <NUM>, <NUM> in a known manner.

In the condition of <FIG>, the actuator means <NUM> are controlled so as to move the rod <NUM> in such a way that the selector <NUM> places itself in the operating condition in which the toothing <NUM> meshes with the toothing <NUM>, thus causing the sleeve <NUM> to be coupled to the rotating structure <NUM>. In this condition, the torque coming from the drive source <NUM> is transmitted from the gearing consisting of the toothed gears <NUM>, <NUM> to the rotating structure <NUM> and to the satellites <NUM>. They rotate between the toothing <NUM> of the sleeve <NUM>, which is fixed to the rotating structure <NUM> and to the toothing <NUM> of the crown <NUM>, and, hence, transmit said torque from the rotating structure <NUM> to the carrier <NUM>, to which they are rigidly connected. The latter splits the torque between the axle shafts <NUM>, <NUM> in a known manner.

Clearly, in the condition of <FIG>, the torque is transmitted according to a different gear ratio compared to condition 8B, in which the torque transmitted to the carrier <NUM> is equal to the torque delivered to the rotating structure <NUM>.

According to the second example embodiment, not according to the present invention shown in <FIG> and <FIG>, the rotating structure <NUM> is coaxial to the axis A of the axle shafts <NUM>, <NUM> and defines a first and a second opening 16a, 16b, which are configured to allow the inner ends 4a, 5a of the axle shafts <NUM>, <NUM> to be inserted inside it.

Preferably, the toothed gear <NUM> is manufactured as a separate piece relative to said portions <NUM>', <NUM>" and is rigidly connected to them. Advantageously, the toothed gear <NUM> is fixed to the portions <NUM>', <NUM>'' by means of the same threaded means connecting them, in particular is arranged on the outside of them, in particular facing the second portion <NUM>".

The planetary <NUM> comprises a plurality of satellites <NUM>, which are connected to the carrier <NUM> of the differential <NUM>, a solar <NUM>, which is housed around one of the axle shafts <NUM>, <NUM>, in the figures the right axle shaft <NUM>, and a crown <NUM>, which is rigidly carried by the rotating structure <NUM>.

In particular, the satellites <NUM> are free to rotate around a pin <NUM> rigidly carried by the carrier <NUM> and, hence, cooperate with a toothing <NUM> defined by the crown <NUM> and with a toothing <NUM> defined by the solar <NUM>. In particular, the pins <NUM> are arranged in an oblique manner relative to the axes A, B described above, advantageously inclined so as to define an acute angle α, whose origin substantially coincides with the central point of the differential <NUM>, namely the symmetry axis of the cross-shaped support <NUM>. In other words, the intersection of the longitudinal axes of the pin <NUM> substantially coincides with the intersection of the rotation axes of the satellites <NUM> of the differential <NUM>.

In particular, according to the embodiment shown herein, the pins <NUM> are manufactured in an integral manner to the carrier <NUM>.

The crown <NUM> is advantageously manufactured as one single piece together with one of the portions <NUM>', <NUM>'', in particular with the first portion <NUM>', and basically comprises the toothing <NUM> axially extending from said portion parallel to the axis A inside the space <NUM>.

In particular, in the case shown herein, the portion of casing <NUM> shown is very small, for clarity reasons, whereas the toothing <NUM> is obtained in the second portion of the rotating structure <NUM>'', in particular in the area of the second opening 16b.

In particular, the actuator means <NUM> are electromechanical actuator means and comprise an electric motor <NUM> configured to operate a worm screw <NUM> meshing with a threaded ring <NUM> rigidly carried by the selector <NUM> and configured to move it along the axis A depending on the rotation of the worm screw <NUM>.

In the condition of <FIG>, the actuator means <NUM> are controlled so as to move the screw <NUM> in such a way that, by meshing with the ring <NUM>, it moves the selector <NUM> to the operating condition in which the toothing <NUM> meshes with the toothing <NUM>, thus causing the sleeve <NUM> to be coupled to the rotating structure <NUM>. In this condition, the torque coming from the drive source <NUM> is transmitted from the gearing consisting of the toothed gears <NUM>, <NUM> to the rotating structure <NUM> and to the satellites <NUM>. They rotate between the toothing <NUM> of the sleeve <NUM>, which is fixed to the rotating structure <NUM> and to the toothing <NUM> of the crown <NUM>, and, hence, transmit said torque from the rotating structure <NUM> to the carrier <NUM>, to which they are rigidly connected. The latter splits the torque between the axle shafts <NUM>, <NUM> in a known manner.

In the condition of <FIG>, the actuator means <NUM> are controlled so as to move the screw <NUM> in such a way that, by meshing with the ring <NUM>, it moves the selector <NUM> to the operating condition in which the toothing <NUM> meshes with the toothing <NUM>, thus causing the sleeve <NUM> to be coupled to the casing <NUM>. In this condition, the torque coming from the drive source <NUM> is transmitted from the gearing consisting of the toothed gears <NUM>, <NUM> to the rotating structure <NUM> and to the satellites <NUM>. They rotate between the toothing <NUM> of the sleeve <NUM>, which is fixed to the casing <NUM> and to the toothing <NUM> of the crown <NUM>, and transmit said torque to the carrier <NUM>, to which they are rigidly connected. The latter splits the torque between the axle shafts <NUM>, <NUM> in a known manner. Clearly, in the condition of <FIG>, the torque is transmitted according to a different gear ratio compared to condition 8B, in which the torque transmitted to the carrier <NUM> is equal to the torque delivered to the rotating structure <NUM>.

In all embodiments described above, the differential group <NUM> further comprises several functional elements, such as anti-dust rings, spacers, o-rings, threaded elements, splines or bearings configured to allow a correct assembly and operation of the structure schematically disclosed above, which are not discussed in the detail for the sake of brevity.

Furthermore, known differential locking means can be provided, which are not shown herein.

Owing to the above, the advantages of a differential group <NUM> according to the invention are evident.

In particular, the differential group <NUM> allows for two possible gear ratios between the drive source <NUM> and the differential <NUM>, thus increasing the versatility of the driving system of the heavy vehicle. In this way, it is possible to provide a versatile differential group for different types of driving styles and loads of the vehicle.

Furthermore, the differential group <NUM> is particularly compact thanks to the specific arrangement of the elements that are part of the rotating structure <NUM> and of the planetary <NUM>. In particular, all the main gears of the differential group <NUM> are isolated from the outside, since they are wrapped inside the casing <NUM> and the rotating structure <NUM>.

In this way, contaminations from the outside can be avoided, thus increasing the useful life of the differential group.

The specific arrangement of the axes of the pins <NUM> and the fact that the crown is obtained on the inside of the rotating structure <NUM> allow for an extremely compact planetary.

Finally, the differential group <NUM> according to the invention can be subjected to changes and variants, which, though, do not go beyond the scope of protection set forth in the appended claim <NUM>.

For example, it is clear that the actuator means <NUM>, <NUM>, <NUM> can be different and be used in an equivalent manner as well as in combination in any one of the embodiments described above.

Furthermore, the pairs of toothed gears described above can be of any type and dimension. Furthermore, the position of the toothed gear <NUM>, the existence of the selector <NUM> or the direct actuation of the sleeve <NUM> by the actuator means can be changed by combining the different embodiments described herein.

Claim 1:
Differential group (<NUM>) for a heavy vehicle, said differential group (<NUM>) comprising a casing (<NUM>) defining a space (<NUM>), a differential (<NUM>) and a transmission (<NUM>) housed inside said space (<NUM>),
said differential (<NUM>) being configured to divide an input torque from a drive source (<NUM>) to said differential group (<NUM>) to a torque of axle shafts (<NUM>, <NUM>) of said vehicle coaxial around an axis (A),
said transmission (<NUM>) being operatively interposed between said driving source (<NUM>) and said differential (<NUM>) and comprising a rotating structure (<NUM>) carried rotationally free from said casing (<NUM>) and a planetary (<NUM>),
said rotating structure (<NUM>) being operatively interposed between said driving source (<NUM>) and said planetary (<NUM>) and defining a space (<NUM>) housing said planetary (<NUM>) and said differential (<NUM>),
said planetary (<NUM>) comprising:
a solar (<NUM>) rotationally carried around one of the axle shafts (<NUM>, <NUM>) and defining a toothing (<NUM>),
a crown (<NUM>) rigidly carried by said rotating structure (<NUM>) and defining a toothing (<NUM>), and
a plurality of satellites (<NUM>) meshing with said toothing (<NUM>, <NUM>) of said solar (<NUM>) and said crown (<NUM>) and configured to rotate around a pin (<NUM>) rigidly carried by a carrier (<NUM>) of said differential,
said differential group (<NUM>) comprising actuator means (<NUM>, <NUM>, <NUM>) configured to control said solar (<NUM>) so that it assumes a first operating condition in which it is rotationally coupled to said rotating structure (<NUM>) or a second operating condition in the which is rotationally coupled to said casing (<NUM>), characterized in that said solar(<NUM>) comprises a sleeve (<NUM>) operated by said actuator means (<NUM>) to move along said axis (A) and positioned around one of the axle shafts (<NUM>, <NUM>),
said sleeve (<NUM>) also defining a first toothing (<NUM>) and a second toothing (<NUM>) configured respectively to mesh alternately with respective teeth (<NUM>, <NUM>) carried by each pin (<NUM>) of said satellites (<NUM>) and by said carcass (<NUM>) as a function of the position of said sleeve on said axis (A).