Differential device mounted at the end of a hollow input shaft

Abstract

The invention relates to a transmission device (DT) comprising a hollow shaft (1) extending from a first axial end (E1) to a second axial end (E2), the hollow shaft comprising recesses formed in the tubular body at the first axial end, each recess having an opening directed axially to allow mounting at the end near the first axial end E1, the transmission device comprising a differential mechanism (DF) comprising a planet carrier element (2) received in the recesses, and rotated by the hollow shaft, four pinion gears (23, 24) rotatably mounted on the planet carrier, a first and a second side gear (21, 22) meshing with the pinion gears, a differential cover (7) inserted from the outside on the first axial end of the hollow shaft, the differential cover (7) comprising an axial opening (72) configured to allow a first drive shaft to pass therethrough.

Description

[0001] DESCRIPTION

[0002] TITLE OF THE INVENTION: Differential device mounted at the end of a hollow shaft leading

[0003]

[0001] The present invention relates to a differential device mounted at the end of a hollow shaft, a differential device which is in practice simply called a "differential".

[0004]

[0002] This refers to the differential function present on a front or rear motorized axle of a motor vehicle, the differential device comprising one input and two outputs (one for each wheel of the axle considered), the two outputs being able to have different rotational speeds for example when the vehicle follows a curved track.

[0005]

[0003] A difference in the rotational speed of the two outputs is referred to in the trade as 'slip' of the differential. The slip may be moderate when the vehicle travels along a curved road, but it may be more significant when one of the wheels slips, or when one of the wheels locks up under the effect of asymmetrical right-left braking.

[0006]

[0004] As will be seen later, the differential housing proposed here is based on the use of a hollow shaft. This hollow shaft can be short or long, depending on various configurations that will be discussed later. The hollow shaft corresponds to the input of the differential; the hollow shaft is referred to as the 'driving' shaft, while the planetary gears are the driven entities (forming the outputs of the differential).

[0007]

[0005] Some have already proposed installing the differential at the heart of an electric motor rotor in the case of an electric motorization of a train or vehicle axle, as for example taught in documents EP0760549 or US11394270.

[0008]

[0006] However, it turns out that the assembly and accessibility of the differential components located within the motor rotor are particularly problematic. EP0760549 requires axially oriented assembly screws, which considerably increases the overall size. US11394270 requires the mounting of bearings at the location of the differential mechanism, which complicates the structure and assembly of the unit.

[0009]

[0007] There therefore remains a need to propose an improved solution for forming a differential in a hollow shaft, with easy assembly and a simple structure, while seeking an interesting compactness.

[0010]

[0008] To this end, a transmission device is proposed comprising a hollow shaft having a tubular body, extending from a first axial end to a second axial end along a main axis,

[0011] - the hollow shaft comprising housings made in the tubular body at the first axial end,

[0012] - each housing having an opening directed axially opposite to the second axial end to allow for end mounting on the side of the first axial end,

[0013] - the transmission device comprising a differential mechanism including a planet carrier element received directly or indirectly in the housings, and driven in rotation by the hollow shaft, at least two planet gears mounted for rotation on the planet carrier, a first planetary gear and a second planetary gear meshing with the planet gears,

[0014] - a differential cover assembled on the first axial end of the hollow shaft, the differential cover comprising an axial opening configured to allow passage of a first drive shaft which can be rotationally fixed to the first planetary pinion, the hollow shaft being configured to house a second drive shaft up to an axial through opening at a second axial end of the hollow shaft.

[0015]

[0009] Thanks to these arrangements, by means of the clever design of the housings provided at the end of the shaft and the covering of the pinions by the differential cover, the differential function can be formed in a hollow shaft with a simplified assembly.

[0016]

[0010] As will be seen later, the hollow shaft in question can be a rotor shaft of an electric traction machine for an electric vehicle, therefore a so-called long shaft. Conversely, the technique can be applied to a short shaft to form a differential unit not integrated into an electric machine.

[0017]

[0011] The cover closes the end of the hollow shaft, trapping the elements of the differential device at that point. In other words, the end of the hollow shaft and the differential cover together form an equivalent of the differential housing found in a conventional differential.

[0018]

[0012] The differential cover can be mounted by shrink fitting and covers the outer cylindrical wall of the hollow shaft over a substantial area.

[0019]

[0013] The proposed solution forms a particularly compact differential.

[0020]

[0014] According to one application, the rotational speed of the hollow shaft can range from 0 to several thousand revolutions per minute, for example up to 10,000 rpm or even 15,000 rpm. The output shafts, driven respectively by the two planetary gears, can each enter a speed reducer, which in turn, after reduction, drives the wheels.

[0021]

[0015] Put another way, the invention provides that the transmission device comprises a differential mechanism housed inside the hollow shaft. The elements of the differential mechanism are inserted from the first end of the hollow shaft, and the device is closed by inserting the differential cover.

[0022]

[0016] It is noted that the housings may or may not pass through the tubular wall of the shaft. If they do not pass through, they are formed as a counterbore on the radially inner side of the tubular wall.

[0023]

[0017] Regarding terminology, it should be noted that "planetary gears" can be simply called "planetary" and "satellite gears" can be simply called "satellites".

[0024]

[0018] According to an example concerning the assembly of the differential cover on the first axial end of the hollow shaft, said differential cover can be inserted from the outside onto the first axial end of the hollow shaft

[0025]

[0019] According to one embodiment, a planetary stop is provided on which the second planetary bears axially, the first planetary bearing axially on the differential cover.

[0026]

[0020] Thus the two planetary gears and the satellites are sandwiched between the planetary bearing and the differential cover.

[0027]

[0021] The planetary thrust bearing advantageously rests on a shoulder provided for this purpose in the hollow shaft.

[0028]

[0022] This forms a simple assembly. Machining the aforementioned shoulder and housings involves simple and conventional machining operations.

[0023] The differential cover can be inserted by shrink fitting. Alternatively, the differential cover can be retained by a circlip engaged in an external annular groove of the hollow shaft.

[0029]

[0024] It is also possible to use other means of fastening such as welding or bolting to assemble the differential cover around the hollow shaft at the location of its first end.

[0030]

[0025] According to one embodiment, an interposed bearing is provided between each housing and the satellite carrier, for the retrieval and transmission of the torque force.

[0031]

[0026] Advantageously, the bearing has a larger contact surface with the hollow shaft than the contact surface of the satellite carrier element if it were received directly in a housing of the hollow shaft.

[0032]

[0027] Indeed, the thickness of the tubular wall of the shaft is limited, but in contrast, the length of the internal bearing in the bearing tube is longer, which allows the compression and shear forces under torque to be distributed satisfactorily.

[0033]

[0028] According to one embodiment, the bearing has a mushroom shape, with a head received in the respective housing opposite, and a bearing tube around which a satellite is mounted.

[0034]

[0029] According to one embodiment, the head has two straight edges parallel to the axis of the hollow shaft. This shape is easy to machine, and the corresponding straight edge is provided on the sides of each recess in the hollow shaft, thus ensuring a very homogeneous linear contact surface.

[0035]

[0030] According to one embodiment, the bearing tube receives a trunnion from the planet carrier. It can be noted that the bearing surface for good torque transmission is thus optimized.

[0036]

[0031] According to one embodiment, pressure washers are provided on the back of the satellites and planetary gears.

[0037]

[0032] These pressure washers contribute to backlash compensation and promote self-centering during rotation. The pressure washers on the back of the planetary gears contribute to axial backlash compensation, while the pressure washers on the back of the satellite gears contribute to transverse backlash compensation.

[0038]

[0033] According to one embodiment, there are four housings and four satellites, and the satellite carrier element is cross-shaped. In this case, the satellite carrier element comprises four arms and a central core.

[0039]

[0034] The use of 4 satellites makes it possible to optimize the available space and maximize the torque transmitted in the available space.

[0040]

[0035] It is possible to form diametrically opposed housings by a single machining operation.

[0041]

[0036] According to one embodiment, the transmission device is devoid of bearings inside the hollow shaft.

[0042]

[0037] The present invention also relates to an electromotive unit with a rotor which comprises a stack of ferromagnetic sheets and a rotor shaft, the electromotive unit comprising a transmission device as described above, and the hollow shaft of the transmission device is formed by the rotor shaft.

[0043]

[0038] In the case of a radial flux electric machine, we are in the long shaft case.

[0044]

[0039] According to one embodiment, the rotor comprises a stack of ferromagnetic laminations, and the rotor shaft is inserted into the rotor by shrink fitting or by complementary shapes.

[0040] This assembly provides a robust fastening and allows effective transmission of torque through the differential mechanism.

[0045]

[0041] According to one embodiment, the differential mechanism is inscribed within a diameter D1, the diameter D1 corresponding substantially to the internal diameter of the rotor plate stack excluding projections and notches,

[0046]

[0042] According to one embodiment the diameter D1 is less than 62 mm.

[0047]

[0043] According to one embodiment, a bearing is provided outside the hollow shaft, arranged to surround the second planetary gear, in the same axial position, for guiding the transmission device in rotation.

[0048]

[0044] The present invention also relates to a method for assembling a differential transmission device comprising:

[0049]

[0045] - prepare a hollow tree with housings to receive the ends of the satellite carrier branches

[0050] - insert a planetary gear stop,

[0051] - Insert the second planetary gear with a thrust washer on its back into the shaft along the axis until it reaches the planetary gear stop.

[0052] - prepare a sub-assembly including the satellite carrier with the 4 satellite gears and the four bearings,

[0053] - Insert the subset defined above into the hollow tree along the Y1 axis,

[0054] - Insert the first planetary gear with a support washer on the back,

[0055] - Insert the differential cover to close the differential mechanism.

[0056]

[0046] The present invention also relates to a motor vehicle, comprising at least one transmission device as described above, and / or an electromotive unit as described above.

[0057]

[0047] The vehicle in question may be an electric or hybrid vehicle.

[0058]

[0048] The invention will be further detailed by describing non-limiting embodiments, and based on the accompanying figures illustrating variants of the invention, in which:

[0059] - [Fig.1] illustrates a front view of a motorized axle of a motor vehicle, in which the present invention is implemented;

[0060] - [Fig.2] represents an exploded view, illustrating the elements involved in the proposed differential device and also illustrating the device assembly process;

[0061] - [Fig.3] illustrates a partial axial cross-sectional view showing an end area of ​​the hollow shaft with the two planetary gears and the differential cover;

[0062] - [Fig.4] illustrates an exploded local axial cross-sectional view representing part of the satellite carrier equipment;

[0063] - [Fig.5] illustrates in front view a bearing interposed between a housing of the hollow shaft and the satellite carrier element;

[0064] - [Fig.6] illustrates a perspective view of an electric machine rotor shaft, this rotor shaft forming a long hollow shaft in the sense of the present invention, the long hollow shaft receiving the elements of the differential mechanism end by end according to the present invention;

[0065] - [Fig.7] illustrates a perspective view of a short hollow shaft according to a second embodiment within the meaning of the present invention, the short hollow shaft receiving the elements of the differential mechanism end by end according to the present invention; - [Fig.8] illustrates in axial section an example of a configuration including the proposed transmission device, with the output drive shafts and a guidance of the hollow shaft by bearing;

[0066] - [Fig.9] schematically illustrates an exploded electromotor group including a transmission device arranged in the rotor shaft of the electric machine;

[0067] - [Fig.10] shows a cross-sectional view of an example variant of an electric machine rotor shaft housing a differential device.

[0068]

[0049] In the various figures, the same reference numerals designate identical or similar elements. For the sake of clarity, some elements are not necessarily shown to scale.

[0069]

[0050] Figure 1 shows an axle of a motor vehicle, in this case a motorized axle in which an electromotor unit GEM drives right and left wheels referenced 47.

[0070]

[0051] In the illustrated example, this refers to an electric motor in a hybrid or pure electric vehicle.

[0071]

[0052] As will be seen in detail later, the rotor shaft drives a differential device DF, each of whose outputs in turn drives a speed reducer (R1, R2). Each of the reducers R1, R2 includes an output pinion which drives the respective wheel 47 by means of a homokinetic transmission T1, T2 as known per se.

[0072]

[0053] For the purposes of the present invention, the reducers shown above are optional; it is not excluded that the outputs of the differential device may directly drive the wheels.

[0073]

[0054] The reference numeral MEL designates the electric machine with a stator and a rotor, denoted 9. The electric machine operates as a motor or a generator depending on the driving conditions. The illustrated electric machine is radial flux, but the invention can also be applied to an axial flux electric machine.

[0074]

[0055] The reference DT generally designates a transmission device carrying a differential function.

[0075]

[0056] The reference numeral UU designates an electromotive unit comprising the machine and the differential device DF. The reference numeral GEM designates the electromotive group comprising an electromotive unit UU, the left-hand gearbox R1 (hereafter referred to as the first gearbox) and the right-hand gearbox R2 (hereafter referred to as the second gearbox).

[0076]

[0057] Figure 9 illustrates, according to a first embodiment, the position of the differential device DF in the electromotive unit UU relative to the electric machine. The drive shafts are shown in a pre-assembly position; more specifically, the short drive shaft A1 and the long drive shaft A2 are shown.

[0077]

[0058] When the vehicle travels along a curved track, one of the drive shafts rotates faster than the other as known in itself, which causes each satellite pinion to rotate on itself as known, which is called differential slip.

[0078]

[0059] The short drive shaft A1, once assembled, drives the first reducer R1. The long drive shaft A2, once assembled, drives the second reducer R2.

[0079]

[0060] The rotor shaft, denoted 1, is hollow and is configured to house the long drive shaft A2. The rotor shaft 1 is integral with the rotor 9 of the machine.

[0061] The rotational connection between the rotor and the drive shaft can be achieved by a shrink-fitting process. In the illustrated example, grooves 14 are provided in the rotor shaft, which receive internal projections of the rotor's ferromagnetic plates. The grooves and projections cooperate by complementary shapes.

[0080]

[0062] Referring to Figures 2 to 6, the rotor shaft, i.e. the hollow shaft 1, has a tubular body. The hollow shaft 1 extends from a first axial end designated E1 to a second axial end designated E2 along a principal axis Y1.

[0081]

[0063] The hollow shaft 1 includes housings 18 made in the tubular body at the first axial end E1. These housings 18 are intended to receive and drive a planet carrier element 2 forming part of the differential mechanism denoted DF.

[0082]

[0064] Each housing comprises a housing base 180 in the shape of a semicircle and two straight sides 181 parallel to the axis Y1. The housing is open at an opening opposite the housing base.

[0083]

[0065] Each housing can be obtained very simply by a machining operation.

[0084]

[0066] The rotor shaft 1 includes a shoulder 160, forming a stop on the side of the first end.

[0085]

[0067] The transmission device includes a differential mechanism DF. The differential mechanism DF includes a planet carrier element 2 received in the housings 18 via bearings described later. The differential mechanism DF is of the bevel gear type here.

[0086]

[0068] Each housing 18 has an opening (also called a mouth) directed axially opposite the second axial end E2 to allow end mounting on the side of the first axial end E1, in the direction of E2.

[0087]

[0069] The planet carrier element 2 is driven in rotation by the hollow shaft 1. The transmission device comprises four planet gears (23, 24, 25, 26) mounted for rotation on the planet carrier 2. The teeth are inclined at approximately 45°.

[0088]

[0070] The satellite carrier element 2 is cross-shaped with four identical arms. Each arm end includes an end trunnion 27 around which a satellite mounted at that location can rotate.

[0089]

[0071] Each of the branches of the cross-shaped satellite carrier element extends along a local axis denoted WR.

[0090]

[0072] A shoulder 29 forms a stop for the inward insertion of the satellite gear. In each of the arms, a lubrication channel 28 is provided. In addition, an axial oil inlet orifice marked 2H is provided.

[0091]

[0073] The satellite carrier element 2 is made of steel, just like the satellites and planetary gears.

[0092]

[0074] The DT transmission device comprises a first planetary gear 21 and a second planetary gear 22. The teeth are inclined at approximately 45°.

[0093]

[0075] Each planetary gear meshes with the satellite gears. The satellite gears do not mesh with each other; they can rotate independently. They generally rotate coherently relative to each other depending on the differential slip. The torque to be transmitted is distributed across the four satellite gears.

[0076] The first planetary gear 21 is suitable for driving the short drive shaft AI. The second planetary gear 22 is suitable for driving the long drive shaft A2.

[0094]

[0077] The number of satellite gears could be two. Thus, generally, the transmission device comprises at least two satellite gears (23, 24).

[0095]

[0078] A bearing 5 is provided interposed between each housing 18 and the satellite carrier 2. The bearing 5 allows the torque force produced by the rotor and allocated to the rotor shaft to be absorbed.

[0096]

[0079] Each bearing 5 is mounted with a very small clearance, on the order of 100 micrometers, in a respective housing 18.

[0097]

[0080] The bearing 5 can be mushroom-shaped. For example, each bearing 5 comprises a head 52 received in the respective housing opposite, and a bearing tube 51 around which a satellite is mounted.

[0098]

[0081] Each of the bearing heads 52 comprises two straight edges 55 parallel to the main axis Y1 orthogonal to the local axis WR of the bearing tube 50.

[0099]

[0082] Each of the bearings includes a front edge 56 which, once assembled, is flush with the free edge 1a of the shaft.

[0100]

[0083] The head is convex 53 outwards with an entry chamfer 57.

[0101]

[0084] The curvature 54 follows the general profile of the outer wall of the hollow shaft once the bearing is in place.

[0102]

[0085] On the inner side, the head includes an annular flat 59 on which a washer, which is discussed below, rests. The annular flat 59 surrounds the base of the bearing tube.

[0103]

[0086] The bearing tube 51 receives on the inner side a trunnion 27 of the satellite carrier 2 received in an inner bearing 50. Furthermore, the bearing tube receives on the outer side, i.e. on its external cylindrical bearing surface 58, the inner bore of the satellite which can whirl at this point.

[0104]

[0087] Each satellite includes a central bore 44 bearing on the external cylindrical surface 58 of the bearing and a back 45 intended to bear on the annular flat 59 of the bearing with interposition of a washer.

[0105]

[0088] The second planetary gear 22 bears against a front face 61 of an annular planetary thrust bearing 6. The planetary thrust bearing 6 comprises a rear face 62 which bears against a shoulder 160 provided in the hollow shaft.

[0106]

[0089] Advantageously, pressure washers (4,4') are provided on the back of the satellites and planetary gears.

[0107]

[0090] Pressure washers are washers that are not flat at rest. They exhibit a certain elasticity and can return to a flat shape under a compressive force.

[0108]

[0091] The thickness of these washers can be approximately 1 mm.

[0109]

[0092] The 4' pressure washers on the back of the planetary gears contribute to the compensation of axial play.

[0110]

[0093] The pressure washers 4 on the back of the satellites contribute to the compensation of transverse play.

[0111]

[0094] The pressure washers also contribute to the self-centering of the drive shafts during rotation. Furthermore, this allows for the elimination of hysteresis when torque direction changes.

[0112]

[0095] The pressure washers can be made of metal or high-performance Teflon.

[0096] According to one embodiment, the satellite carrier element could be received directly in household housings at the end of the hollow shaft.

[0113]

[0097] Thus, it can be stated that the satellite carrier element 2 is received directly or indirectly in the housings 18.

[0114]

[0098] The invention cleverly proposes to use a differential cover noted 7 inserted externally on the first axial end E1 of the hollow shaft 1.

[0115]

[0099] The differential cover 7 is formed as a metal ferrule with a material thickness between 2 mm and 5 mm, preferably with a material thickness between 3 mm and 4 mm.

[0116]

[0100] The differential cover includes a capping skirt 70 delimited by a free circular border 74.

[0117]

[0101] As seen in the figures, the differential cover 7 includes an axial opening 72 configured to allow passage for the first drive shaft A1 which can be rotationally fixed to the first planetary pinion 21.

[0118]

[0102] Furthermore, the hollow shaft 1 is configured to house the second drive shaft A2 up to an axial through opening noted 19 at the second axial end E2 of the hollow shaft.

[0119]

[0103] The differential cover 7 is inserted onto the hollow shaft until the internal annular bearing 76 comes into contact with the free end 1a of the hollow shaft, as seen in figure 3.

[0120]

[0104] The differential cover 7 can be inserted by shrink fitting onto the hollow shaft 1.

[0121]

[0105] The overlap length LF (see figure 8) is substantial, which allows for a very solid fixing of the differential cover on the hollow shaft.

[0122]

[0106] Alternatively, the differential cover can be retained by a circlip engaged in an external annular groove of the hollow shaft.

[0123]

[0107] It is also possible to use other means of fastening such as welding, for example laser welding, to assemble the differential cover around the hollow shaft at the location of its first end.

[0124]

[0108] The wound rotor is electrically activated via excitation tracks P1, P2. The excitation tracks are arranged in an annular manner at the second end E2 of the shaft opposite the position of the differential device.

[0125]

[0109] It is noted that the DT transmission device is devoid of bearings inside the hollow shaft, which makes it possible to increase the compactness of the differential mechanism.

[0126]

[0110] The bearing B1 is arranged to surround the second planetary gear 22, in the same axial position, for guiding the rotation of the transmission device

[0127]

[0111] The hollow shaft 1 is equipped with a shim ring marked 12.

[0128]

[0112] It is noted with reference to figure 10 that at the first end of the hollow shaft, the outside diameter can be slightly increased, namely D1' to accommodate the differential mechanism at this location, DT exceeds D1 by 2 to 4mm.

[0129]

[0113] Turning now to Figure 7, we have represented a differential unit DT whose structure and mounting principle are similar or identical to that described above for the case of a long shaft, but here it is a short shaft.

[0130]

[0114] The hollow shaft 1 can be fitted with a drive ring represented by the flange 1c, which can contain an input gear. Otherwise, the first end E1 of the shaft is retained, with the housings provided to receive the bearings, the planet carrier element, and the planets, as already described for the first embodiment and therefore not described again here.

[0115] The differential unit proposed here can be used as a conventional differential in a vehicle axle drivetrain.

[0131]

[0116] Regarding the relative dimensions, it is noted that in the first embodiment, we have D1 / L9 < 0.5 where L9 is the axial length of the rotor. We also have D1 / D9 < 0.4 where D9 is the diameter of the rotor. The diameter D1 is therefore small, even though the rotor shaft houses the differential mechanism.

[0132]

[0117] Furthermore, we can have D1 / DM < 0.25 where DM is the diameter of the electrical machine MEL (see figure 9).

[0133]

[0118] The electromotive unit UU therefore integrates the differential function in a form factor which differs very little from a form factor of an electric machine alone for the same power characteristics.

[0134]

[0119] According to a particular application example on a motor vehicle drive axle, D1 < 62 mm for a motor torque to be passed up to the order of 800 Nm.

[0135]

[0120] As a typical example, the reduction ratio provided by each of the reducers is close to 10, and the rotational speeds of the differential are therefore approximately 10 times greater than the rotational speeds of the vehicle's wheels. Consequently, the torque passing through the differential is relatively low compared to the torque applied to a differential located downstream of a single reducer.

[0136]

[0121] Moreover, the slippage is limited by software functions.

[0137]

[0122] According to an advantageous arrangement, the slippage of the differential device is limited by the general behavior of the system and in general and in particular by the intervention of software which makes it possible to drastically reduce the torque and therefore the rotational speed of the motor in the event that one of the wheels slips.

[0138]

[0123] As known per se, it is provided as a position and rotation speed sensor for the rotor, not shown in the figures.

[0139]

[0124] The combination described above allows the differential device to be sized as precisely as possible and to be housed inside a rotor shaft of an electric machine, here on one end of this shaft opposite the electrical excitation tracks when the rotor is wound.

Claims

DEMANDS 1. Transmission device (TD) comprising a hollow shaft (1) having a tubular body, extending from a first axial end (E1) to a second axial end (E2) along a main axis (Y1), - the hollow shaft comprising housings (18) made in the tubular body at the first axial end (E1), - each housing having an opening directed axially opposite to the second axial end (E2) to allow end mounting on the side of the first axial end (E1), - the transmission device comprising: - a differential mechanism (DF) comprising a planet carrier element (2) received directly or indirectly in the housings (18), and driven in rotation by the hollow shaft, at least two planet gears (23,24) mounted for rotation on the planet carrier, a first planetary gear (21) and a second planetary gear (22) meshing with the planet gears, - a differential cover (7) assembled on the first axial end of the hollow shaft, the differential cover (7) comprising an axial opening (72) configured to allow passage of a first drive shaft (A1) which can be rotationally fixed to the first planetary pinion (21), the hollow shaft (1) being configured to house a second drive shaft (A2) up to an axial through opening at a second axial end (E2) of the hollow shaft.

2. Transmission device according to claim 1, in which a planetary stop (6) is provided on which the second planetary (22) bears axially, the first planetary (21) bearing axially on the differential cover (7).

3. Transmission device according to claim 1, in which a bearing (5) is provided interposed between each housing and the satellite carrier (2), for retrieval and transmission of the torque force.

4. Transmission device according to claim 1, in which the bearing has a mushroom shape, with a head (52) received in the respective housing and a bearing tube (51) around which a satellite is mounted.

5. Transmission device according to any one of claims 1 to 4, wherein pressure washers (4,4') are provided on the back of the satellites and planetary gears.

6. Transmission device according to any one of claims 1 to 5, comprising four housings (18) and four satellites (23,24,25,26), and the satellite carrier element (2) is cross-shaped.

7. Electromotive unit (EMU) comprising an electric machine (EM) with a rotor (9) and a rotor shaft (1), the electromotive unit comprising a device transmission (DT) according to any one of claims 1 to 6, wherein the hollow shaft of the transmission device is formed by the rotor shaft.

8. Electromotive unit according to claim 7, wherein the rotor comprises a stack of ferromagnetic laminations, and the rotor shaft (1) is inserted into the rotor by shrink fitting or by complementary shapes.

9. Electromotive unit according to claim 7, in which the differential mechanism is inscribed in a diameter D1, the diameter D1 corresponding substantially to the internal diameter of the rotor plate stack excluding projections and notches, the diameter D1 preferably being less than 62 mm.

10. Motor vehicle, preferably electric or hybrid, comprising a transmission device according to any one of claims 1 to 6, or an electromotive unit according to any one of claims 7 to 9.

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