Electromotive assembly for a vehicle axle with a differential and two reduction gears

Abstract

Disclosed is an electromotive assembly (GEM) comprising: an electric machine with a wound rotor (9) and a tubular rotor shaft (1) extending from a first axial end (E1) to a second axial end (E2) along a main axis, the rotor shaft comprising excitation tracks (P1, P2) arranged on the rotor shaft at the second end of said rotor shaft; a differential mechanism (DF) arranged at the first end of the rotor shaft, the differential mechanism comprising a planet carrier element (2) driven by the rotor shaft and rotating at the same speed as the rotor shaft, at least two pinion gears (23, 25) carried on the planet carrier element, and sun gears (21, 22) meshing with the pinion gears; a first, short auxiliary shaft (A1), linked to the first sun gear (21), and a second, long auxiliary shaft (A2), linked to the second sun gear (22); a first reduction gear (R1) driven by the short auxiliary shaft, and a second reduction gear (R2), driven by the long auxiliary shaft.

Description

[0001] DESCRIPTION

[0002] TITLE OF THE INVENTION: Electromotor unit for vehicle axle with a differential and two reduction gears

[0003]

[0001] The present invention relates to an electromotor unit for a vehicle axle, said electromotor unit comprising an electric machine, a differential and two reducers.

[0004]

[0002] When discussing the differential function present on a front or rear powered axle of a conventional motor vehicle, the differential device comprises one input and two outputs, and each of the two outputs drives one of the axle's wheels via one or more constant velocity joints. There is generally a reduction gear between the electric motor and the differential input. Therefore, there is only one reduction gear per axle in these configurations. In other words, the reduction gear is located upstream of the differential in the drivetrain.

[0005]

[0003] The differential device must be sized to accommodate a significant torque, and its components must be sized accordingly. This makes the differential bulky and expensive.

[0006]

[0004] This bulk is unfavorable to good integration into the vehicle architecture and the differential occupies a space that could be allocated to other functions, including increasing the storage compartment volume.

[0007]

[0005] Among the ideas for improving the size and increasing the integration capacity of the electric motor-based unit, one can consider the idea of ​​moving the differential function to the motor output and placing a reduction gear on each of the differential outputs. Since the differential rotates faster, the torque it must transmit is therefore lower, and its mechanical dimensions allow for a reduced size.

[0008]

[0006] Some have already proposed installing the differential in the electric motor rotor, upstream of gearboxes in the case of electric drive for a train or vehicle axle, as taught, for example, in document US11394270. However, it should be noted that US11394270 uses a permanent magnet rotor requiring the use of rare materials, and also uses planetary gear reducers. The maximum reduction ratio offered by a planetary gear train is approximately 9, and planetary gear reducers are expensive.

[0009]

[0007] There therefore remains a need to propose a more relevant solution from an economic and ecological point of view.

[0010]

[0008] To this end, an electromotor unit comprising is proposed here:

[0011] - an electrical machine with a wound rotor and a rotor shaft extending from a first axial end to a second axial end along a main axis, the rotor shaft being hollow and tubular in shape, the rotor shaft comprising:

[0012] - excitation tracks arranged annularly on the rotor shaft at the second end of the rotor shaft,

[0013] - a differential mechanism arranged near the first end of the rotor shaft, the differential mechanism comprising a planet carrier element driven by the rotor shaft and rotating at the same speed as the rotor shaft, at least two planet gears mounted on the planet carrier element, a first planetary gear and a second planetary gear meshing with the planet gears,

[0014] - a first short intermediate shaft, rotationally linked to the first planetary gear, and a second long intermediate shaft, rotationally linked to the second planetary gear,

[0015] - a first reducer driven by the short intermediate shaft, and a second reducer, driven by the long intermediate shaft.

[0016]

[0009] Thanks to these arrangements, it is cleverly proposed to use one end of the rotor shaft to place the electrical excitation of the wound rotor and to use the other end of the rotor shaft to place the differential directly downstream of the rotor shaft and upstream of the reducers.

[0017]

[0010] The compact size of such an assembly proves particularly advantageous and facilitates its integration into various vehicle architectures, the said vehicles then being able to offer larger storage spaces.

[0018]

[0011] The reduction ratio provided by each of the reducers is significant, for example close to 10, and the rotational speeds of the differential are therefore much higher, for example 10 times higher than the rotational speeds of the vehicle's wheels. It follows that the torque passing through the differential is relatively low, and the dimensions can also be significantly reduced compared to the conventional case downstream of the reducer.

[0019]

[0012] Put another way, the differential is small in size and rotates quickly.

[0020]

[0013] Depending on the application, the rotational speed of the rotor 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]

[0014] Regarding terminology, the term 'in the vicinity' in the phrase 'differential mechanism arranged in the vicinity of the first end of the rotor shaft', should be interpreted as meaning that the differential mechanism is in the vicinity of the first end, for example less than 50 mm from the first end, or as meaning that the differential mechanism is directly at the first end as will be seen in examples illustrated later.

[0022]

[0015] Regarding terminology, it should be noted that "planetary gears" can be simply called "planetary" and "satellite gears" can be simply called "satellites".

[0023]

[0016] It is noted that the differential can be of the bevel gear type or can be a differential of the so-called 'Torsen' type.

[0024]

[0017] It is noted that at this stage, the reducers can be epicyclic gear trains or cascade gears.

[0025]

[0018] According to an advantageous embodiment, the reducers are gear cascade reducers. The cost of these reducers is particularly attractive. Furthermore, the reduction ratio is within a very wide range, for example from 6 to 20; it is simply a matter of adjusting the center distance of the gears to obtain the desired ratio. There is no structural limitation that is common to epicyclic gear reducers.

[0019] According to one embodiment, each of the first and second reducers comprises a single reduction stage. This configuration proves to be simple, reliable, and inexpensive.

[0026]

[0020] According to one embodiment, each of the first and second reducers has a reduction ratio between 6 and 15.

[0027]

[0021] A wide range of possible ratios is available, to be chosen according to various vehicle and engine configurations.

[0028]

[0022] According to one embodiment, it is provided that for each of the first and second reducers, the input and output are coaxial.

[0029]

[0023] Advantageously, the integration of such an electric motor unit into the vehicle architecture is facilitated. In practice, a slender form factor along the main axis allows for greater possibilities for integrating the electric motor unit into the vehicle architecture.

[0030]

[0024] Such a coaxial arrangement helps to avoid certain parasitic torques, particularly during torque transients. The design of the anti-torque support buffers is simplified.

[0031]

[0025] According to one embodiment, each of the first and second reducers comprises an input pinion, a high-speed gear, a low-speed gear, the low-speed gear comprising a toothed output hub.

[0032]

[0026] The fast gear includes a first toothed sector of large diameter and a second toothed sector of small diameter which drives a first toothed sector of large diameter of the slow gear.

[0033]

[0027] According to one embodiment, the center distance separating the axis of the high-speed gear from the axis of the low-speed gear is between 100 mm and 130 mm.

[0034]

[0028] A reduction ratio of 10 to 12 can be obtained, which is higher than what can be obtained using an epicyclic gear reducer.

[0035]

[0029] According to one embodiment, the electric machine can be interposed between the two reducers, the housings of the two reducers being fixed to the housing of the electric machine in order to form a single assembled unit.

[0036]

[0030] Such a unit can be prepared as a sub-assembly for mounting on a rolling platform or under the vehicle body. Furthermore, and advantageously, there is no need for external shafts to connect the electromotive unit and each of the gearboxes.

[0037]

[0031] According to one embodiment, the first and second reducers are identical, the second reducer being rotated 180° relative to the first reducer.

[0038]

[0032] This reduces industrial diversity.

[0039]

[0033] According to one embodiment, the differential mechanism is arranged at least partially in an axial area of ​​the rotor. This contributes to reducing the overall size and improving the compactness of the electro-motor unit.

[0040]

[0034] In practice, the differential mechanism is housed at least partly inside the rotor shaft.

[0041]

[0035] According to one embodiment, the differential mechanism is substantially contained within the diameter D1, where D1 is the outer diameter of the rotor shaft. The presence of the differential mechanism does not significantly increase the axial and radial dimensions of the motor.

[0042]

[0036] According to one embodiment the diameter D1 is less than 62 mm.

[0043]

[0037] According to one embodiment, the excitation tracks have an outside diameter D5 between 36 mm and 42 mm, and the minimum inside diameter D0 of the rotor shaft in a region of the second end E2 is at least equal to 25 mm, preferably at least equal to 28 mm.

[0038] This combination of diametral dimensions constitutes an optimum for maintaining a tangential friction speed of the excitation pads on the excitation tracks within an acceptable range, and at the same time allowing the passage of the long intermediate shaft completely inside the rotor shaft, while preventing this long intermediate shaft from exhibiting too much torsional elasticity given its length.

[0044]

[0039] The present invention also relates to a motor vehicle, comprising at least one electromotor unit as described above.

[0045]

[0040] The vehicle in question may be an electric or hybrid vehicle.

[0046]

[0041] The invention will be further detailed by describing non-limiting embodiments, and based on the accompanying figures illustrating variants of the invention, in which:

[0047] - [Fig.1] illustrates a front view of a first example of a motorized axle of a motor vehicle, in which the present invention is implemented;

[0048] - [Fig.2] illustrates a front view of a second example of a motorized axle of a motor vehicle, in which the present invention is implemented;

[0049] - [Fig.3] schematically represents in cross-section the electromotor unit according to the first example of axle in figure 1;

[0050] - [Fig.4] schematically represents in section and exploded view the electromotor unit according to the second axle example of figure 2;

[0051] - [Fig.5] schematically represents in cross-section and in more detail the electromotor unit according to the second axle example of figure 2;

[0052] - [Fig.6] shows a cross-sectional view of an example of an electric machine rotor shaft housing a differential device at one end;

[0053] - [Fig.7] illustrates a perspective view of an electric machine rotor shaft, this rotor shaft receiving the elements of the differential mechanism end to end;

[0054] - [Fig.8] represents an exploded view, illustrating the elements involved in the proposed differential device and also illustrating the device assembly process;

[0055] - [Fig.9] illustrates in cross-sectional view the two ends of a machine rotor shaft with electrical, with on the right the electrical excitation system of the wound rotor and on the left the differential device, and the short and long intermediate shafts.

[0056]

[0042] 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.

[0057]

[0043] 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 according to a first embodiment.

[0058]

[0044] In the illustrated example, this refers to an electric motor in a hybrid or pure electric vehicle.

[0059]

[0045] 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 comprises an output pinion that drives the respective wheel 47 by means of a constant velocity transmission T1, T2, as known per se.

[0046] 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.

[0060]

[0047] The reference numeral GEM designates the electromotor unit comprising the electric machine MEL, the differential device DF, the left-hand reduction gear R1 (hereafter referred to as the first reduction gear), and the right-hand reduction gear R2 (hereafter referred to as the second reduction gear). The differential device DF can be of any known type. The differential device DF is located in the vicinity of the electric machine and is driven directly by the rotor shaft. The differential device DF can be positioned at the end of the shaft, adjacent to it, or a few millimeters or even tens of millimeters away.

[0061]

[0048] Figure 2 shows a similar device, except that the differential device is integrated into a unit called the electromotive unit UU. The differential device is then specific and will be discussed in more detail later.

[0062]

[0049] The reference numeral UU designates an electromotive unit comprising the electric machine and the differential device DF. The reference numeral GEM designates the electromotive group comprising the electromotive unit UU, the left-hand gearbox R1 (first gearbox), and the right-hand gearbox R2 (second gearbox). Here, the differential device DF is integrated, at least partially, into the rotor shaft. The differential device DF is therefore located at the first end of the rotor shaft.

[0063]

[0050] In the case of Figure 1 as well as in the case of Figure 2, the differential device DF is located directly downstream of the rotor shaft of the electric machine, whether it is integrated or in the immediate vicinity.

[0064]

[0051] Figure 3 illustrates, according to the first embodiment, the position of the differential device DF in the electromotive unit UU relative to the electric machine. The intermediate drive shafts are shown in a pre-assembly position; more specifically, the short intermediate shaft A1 and the long intermediate shaft A2.

[0065]

[0052] When the vehicle travels along a curved track, one of the intermediate drive shafts rotates faster than the other as known per se, which causes each satellite pinion to rotate on itself as known, which is called differential slip.

[0066]

[0053] The short intermediate shaft A1, once assembled, drives the first reducer R1 via the first input pinion of the reducer, marked 31. The long intermediate shaft A2, once assembled, drives the second reducer R2 via the second input pinion of the reducer, marked 32.

[0067]

[0054] The rotor shaft noted 1 is hollow and is configured to house the long intermediate shaft A2. The rotor shaft 1 is integral with the rotor 9 of the machine.

[0068]

[0055] The rotational locking of 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.

[0069]

[0056] In general, the differential device can be of any type, for example it can be a bevel gear differential, it can be a 'Torsen' type differential.

[0070]

[0057] Referring to Figures 4 to 8, the rotor shaft, i.e., rotor shaft 1, has a tubular body. The rotor shaft 1 extends from a first axial end designated E1 to a second axial end designated E2 along a principal axis designated Y1.

[0071]

[0058] The rotor 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.

[0072]

[0059] The rotor shaft 1 has in its main part an outside diameter D1 over a length denoted L1, as seen in figure 7.

[0073]

[0060] The rotor shaft 1 is mounted to rotate around Y1 relative to the machine housing CM by means of two bearings B1 and B2.

[0074]

[0061] The rotor shaft 1 includes a shoulder 160, forming a stop on the side of the first end.

[0075]

[0062] The differential mechanism DF comprises 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.

[0076]

[0063] Each housing 18 has an opening directed axially opposite to the second axial end E2 to allow end mounting on the side of the first axial end E1, in the direction of E2.

[0077]

[0064] The planet carrier element 2 is driven in rotation by the rotor shaft 1. The transmission device includes four planet gears (23, 24, 25, 26) mounted for rotation on the planet carrier 2.

[0078]

[0065] The satellite carrier element 2 is cross-shaped with four identical arms. Each end includes an end trunnion 27 around which a satellite mounted at that location can rotate.

[0079]

[0066] Each of the branches of the cross-shaped satellite carrier element extends along a local axis perpendicular to the main axis.

[0080]

[0067] The satellite carrier element 2 is made of steel, just like the satellites and planetary gears.

[0081]

[0068] The differential mechanism DF comprises a first planetary pinion 21 and a second planetary pinion 22.

[0082]

[0069] Each planetary gear meshes with the satellite gears. The satellite gears do not mesh with each other.

[0083]

[0070] The first planetary gear 21 is suitable for driving the short intermediate shaft A1. The second planetary gear 22 is suitable for driving the long intermediate shaft A2.

[0084]

[0071] The number of satellite gears could be two. Thus, generally, the transmission device comprises at least two satellite gears.

[0085]

[0072] A bearing 5 is provided interposed between each housing 18 and the satellite carrier 2. The bearing 5 allows the torque produced by the rotor to be taken up and transferred to the rotor shaft via the differential device.

[0086]

[0073] The bearing 5 can be mushroom-shaped. For example, each bearing 5 comprises a head received in the respective opposite housing, and a bearing tube around which a satellite is mounted.

[0087]

[0074] Each of the bearing heads comprises two straight edges 55 parallel to the main axis Y1 orthogonal to the local axis of the bearing tube.

[0088]

[0075] Each of the bearings includes a front edge 56 which, once assembled, is flush with the free edge 1a of the shaft.

[0089]

[0076] The head is convex outwards with an entry chamfer.

[0090]

[0077] The curvature follows the general profile of the outer wall of the rotor shaft once the bearing is in place.

[0078] On the inner side, the head includes an annular flat on which a washer rests. The annular flat surrounds the base of the bearing tube.

[0091]

[0079] The bearing tube receives on its inner side a trunnion 27 of the planet carrier 2 which is received in an internal bearing. Furthermore, the bearing tube receives on its outer side, i.e. on its external cylindrical surface, the inner bore of the planet carrier which can rotate at this point.

[0092]

[0080] Each housing comprises a semicircular housing base 180 and two straight sides 181 parallel to the axis Y1. The housing is open at an opening opposite the housing base. Each housing can be easily obtained by a milling cutter.

[0093]

[0081] 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 rotor shaft.

[0094]

[0082] Advantageously, pressure washers (4,4') are provided on the back of the satellites and planetary gears.

[0095]

[0083] Pressure washers are non-flat washers at rest. They exhibit a certain elasticity and can return to a flat shape under compressive stress. The pressure washers 4' on the back of the planetary gears contribute to compensating for axial play. The pressure washers 4 on the back of the satellite gears contribute to compensating for transverse play. The pressure washers also contribute to the self-centering of the drive shafts during rotation. Furthermore, this allows hysteresis to be eliminated when the direction of torque changes.

[0096]

[0084] The invention cleverly proposes to use a differential cover noted 7 inserted externally on the first axial end E1 of the rotor shaft 1.

[0097]

[0085] 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.

[0098]

[0086] The differential cover includes a covering skirt 70 delimited by a free circular border 74.

[0099]

[0087] As can be seen in the figures, the differential cover 7 includes an axial opening 72 configured to allow passage for the first intermediate shaft A1 which can be rotationally fixed to the first planetary pinion 21.

[0100]

[0088] Furthermore, the rotor shaft 1 is configured to house the second intermediate shaft A2 up to an axial through opening noted 19 at the second axial end E2 of the rotor shaft.

[0101]

[0089] The differential cover 7 is inserted onto the rotor shaft until the internal annular bearing comes into contact with the free end 1a of the rotor shaft, as seen in Figure 3.

[0102]

[0090] The differential cover 7 can be inserted by shrink fitting onto the rotor shaft 1.

[0103]

[0091] The wound rotor is electrically activated via excitation tracks P1, P2. The excitation tracks are arranged in an annular fashion at the second end E2 of the shaft opposite the position of the differential device. The excitation tracks have an outer diameter denoted D5 as illustrated in Figures 6 and 9.

[0104]

[0092] The excitation tracks are arranged on an insulating ring designated 48.

[0093] The excitation tracks are conductive, for example made of copper alloy. Opposite each track, one or more friction pads (not shown) are provided which make contact with the track and are pushed towards the track by an elastic system.

[0105]

[0094] The tangential contact speed of friction between the pad and the rotating track is proportional to the rotor's rotational speed. In one embodiment, the tangential speed is desired to be less than 40 m / s. In the electrical machines considered here, the return can rotate at high speeds, up to 15,000 rpm, or even up to 20,000 rpm in extreme cases.

[0106]

[0095] It follows that the diameter D5 must be as small as possible. However, this requirement is contradictory to the need to allow the long intermediate shaft A2 to pass through an axial opening.

[0107]

[0096] In typical applications, D5 can be chosen to be between 36 mm and 42 mm, and the minimum inner diameter D0 of the rotor shaft in a region of the second end E2 can be at least 25 mm, preferably at least 28 mm. This represents an optimal compromise for having a sufficiently robust rotor shaft 1, which allows the long intermediate shaft A2 to pass through its center and on which the insulating ring 48 with the excitation tracks P1, P2 can be mounted.

[0108]

[0097] The outside diameter D20 of the long intermediate shaft A2 is chosen to be around 25 mm, for example, within a range of values ​​between 22 and 26 mm. It should be noted that, depending on one option, the long intermediate shaft A2 has an axial lubrication passage along its entire length.

[0109]

[0098] It is noted that the transmission device is devoid of bearings inside the rotor shaft, which makes it possible to increase the compactness of the differential mechanism.

[0110]

[0099] The bearing B1 is arranged to surround the second planetary 22, in the same axial position, for rotational guidance of the transmission device and in particular for guiding the rotor shaft.

[0111]

[0100] The bearing B1 is received in a seat of the front housing C1 of the MEL machine.

[0112]

[0101] The electric machine includes a housing CM, composed here of three parts: a main housing C0 in the shape of a sleeve, a first end housing C1 and a second end housing C2.

[0113]

[0102] The axial length of the electromotor group is denoted LG (see figure 5).

[0114]

[0103] The rotor shaft 1 is equipped with a shim ring marked 12.

[0115]

[0104] Reducers

[0116]

[0105] The first reducer R1 includes a reducer housing marked CR1.

[0117]

[0106] The first reducer R1 comprises an input pinion 31, a high-speed gear 41, a low-speed gear 42, the low-speed gear comprising a toothed output hub, into which a toothed shaft end of the homokinetic transmission 61 is inserted to a wheel (see figure 5).

[0118]

[0107] The input pinion 31 is guided in rotation by a bearing B3.

[0119]

[0108] The center distance separating the axis of the high-speed gear 41 from the main axis Y1 is denoted ER and is here between 100 mm and 130 mm. This is the same center distance that separates the axis of the high-speed gear 41 from the axis of the low-speed gear 42.

[0120]

[0109] Indeed, advantageously, the input and output of the first reducer are coaxial, on the Y1 axis.

[0121]

[0110] The shaft of the high-speed gear 41 is guided in rotation by a bearing B5 and a bearing B7.

[0111] The low-speed gear 42 forms the output of the reducer.

[0122]

[0112] The shaft of the slow gear 42 is guided in rotation on the output side by a bearing B6 and on the opposite side by a needle bearing N1 mounted on an inner bearing of the input pinion 31 (see figure 5).

[0123]

[0113] The high-speed gear 41 comprises a first toothed sector of large diameter 41a, radially external, and a second toothed sector of small diameter 41b, radially external, which drives a first toothed sector of large diameter 42a of the low-speed gear 42, radially external.

[0124]

[0114] The slow gear 42 includes radially internal splines noted 42b to receive the end of the constant velocity joint 61.

[0125]

[0115] The second reducer R2 comprises an input pinion 32, a high-speed gear 41, a low-speed gear 42, the low-speed gear comprising a toothed output hub, into which a toothed shaft end of the homokinetic transmission 62 is inserted towards the other wheel.

[0126]

[0116] The input pinion 32 is guided in rotation by a bearing B4.

[0127]

[0117] The second reducer R2 includes a reducer housing marked CR2.

[0128]

[0118] The second reducer R2 is similar or even identical to the first reducer and the description made for the first reducer applies to the second reducer R2.

[0129]

[0119] Advantageously, two identical reducers can be used, one being rotated 180° relative to the other around an axis perpendicular to Y1.

[0130]

[0120] It is noted that each reducer includes five bearings (four ball bearings B3, B5, B6, B7 and one needle bearing N1) to guide in rotation three rotating parts namely the input pinion, the high-speed gear and the low-speed gear.

[0131]

[0121] Gear cascade reducers are very reliable and inexpensive. Smaller cascade reducers than those shown in the figures could be used.

[0132]

[0122] Each reducer housing is formed in two parts as can be seen in figures 4 and 5.

[0133]

[0123] Each CR1,CR2 gearbox housing is fixed to the CM machine housing at one end.

[0134]

[0124] Once the assembly is complete, the MEL electric machine is interposed between the two reducers. The housings of the two reducers (CR1, CR2) are fixed to the CM housing of the electric machine to form a single assembled mechanical unit.

[0135]

[0125] 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.

[0136]

[0126] Furthermore, we can have D1 / DM < 0.25 where DM is the diameter of the electrical machine MEL (see figure 5).

[0137]

[0127] The outside diameter of the first intermediate shaft A1 is constant along its length and is denoted D10 (see Figure 9). D10 can be, for example, between 16 mm and 20 mm. The first intermediate shaft A1 may have splines along its entire length. The end portions of the second intermediate shaft A2 may also have an outside diameter of D10 with splines identical to those of A1.

[0128] It should be noted that the electromotive unit UU integrates the differential function into a form factor that differs very little from the form factor of a standalone electric machine for the same power characteristics.

[0138]

[0129] 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.

[0139]

[0130] According to 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. It follows that the torque passing through the differential is relatively low compared to the torque applied to a differential located downstream of a single reducer.

[0140]

[0131] Moreover, the slippage is limited by software functions.

[0141]

[0132] 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.

[0142]

[0133] As known per se, it is provided as a position and rotation speed sensor for the rotor, not shown in the figures.

[0143]

[0134] 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.

[0144]

[0135] It is noted with reference to Figure 6 that at the first end of the rotor shaft, the outside diameter can be slightly increased, namely DT, to accommodate the differential mechanism at that location.

Claims

DEMANDS 1. Electric motor unit (EMU) comprising: - an electrical machine with a wound rotor (9) and a rotor shaft (1) extending from a first axial end (E1) to a second axial end (E2) along a main axis (Y1), the rotor shaft being hollow and tubular in shape, the rotor shaft comprising: - Excitation tracks (P1, P2) arranged annularly on the rotor shaft at the second end of the rotor shaft, - a differential mechanism (DF) arranged in the vicinity of the first end of the rotor shaft, the differential mechanism comprising a planet carrier element (2) driven by the rotor shaft and rotating at the same speed as the rotor shaft, at least two planet gears (23, 25) carried on the planet carrier element, a first planetary gear (21) and a second planetary gear (22) meshing with the planet gears, - a first short intermediate shaft (A1), rotationally linked to the first planetary gear (21), and a second long intermediate shaft (A2), rotationally linked to the second planetary gear (22), - a first reducer (R1) driven by the short intermediate shaft (A1), and a second reducer (R2), driven by the long intermediate shaft (A2).

2. Electromotor unit according to claim 1, wherein the first and second reducers are gear cascade reducers, preferably with each of the first and second reducers comprising a single reduction stage, preferably with a reduction ratio between 6 and 15.

3. Electromotor set according to any one of claims 1 to 2, wherein for each of the first and second reducers, the input and output are coaxial.

4. Electromotor unit according to any one of claims 1 to 3, wherein each of the first and second reducers comprises an input pinion (31, 32), a high-speed gear (41), a low-speed gear (42), the low-speed gear comprising a toothed output hub, preferably with a center distance (ER) separating the axis of the high-speed gear from the axis of the low-speed gear is between 100 mm and 130 mm.

5. Electromotor unit according to any one of claims 1 to 5, in which the electric machine is interposed between the two reducers, the housings (CR1, CR2) of the two reducers being fixed to the housing (CM) of the electric machine in order to form a single assembled unit.

6. Electromotor unit according to any one of claims 1 to 6, wherein the first and second reducers are identical, the second reducer (R2) being rotated 180° relative to the first reducer (R1).

7. Electromotor unit according to any one of claims 1 to 7, wherein the differential mechanism (DF) is arranged at least partly in a rotor axial zone.

8. Electromotor unit according to any one of claims 1 to 8, in which the differential mechanism (DF) is substantially inscribed in the diameter D1, D1 being the outside diameter of the rotor shaft.

9. Electromotor unit according to any one of claims 1 to 8, wherein the excitation tracks have an outside diameter D5 between 36 mm and 42 mm, and the minimum inside diameter DO of the rotor shaft in a region of the second end (E2) is at least equal to 25 mm, preferably at least equal to 28 mm.

10. Motor vehicle, preferably electric or hybrid, comprising an electric motor unit (EMU) according to any one of claims 1 to 9.

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