Transmission assembly in a motor vehicle, having a locking device

Abstract

The invention relates to a locking device for a driveline transmission in a vehicle, comprising: an electric motor (6) having a rotor (60) having an axis (A1); a first pinion (21) that rotates integrally with the rotor; a countershaft (2) fitted to rotate about a second axis (A2) and equipped with a second pinion (22) and a third pinion (23), the second pinion meshing with the first pinion; an output ring gear (3) meshing with the third pinion and in a kinematic relationship with the wheels of the vehicle; a locking sleeve (1) centered on a first axis and axially displaceable between an unlocked position (P1) and a locked position (P2); a shift fork (4) for axially displacing the locking sleeve between an unlocked position and a locked position in which the locking sleeve directly rotationally connects the first pinion to the output ring gear.

Description

[0001] This invention relates to a transmission assembly in a motor vehicle, the transmission assembly including a locking device designed to lock the drive chain used for the axle or wheels. The invention particularly relates to vehicle axles (for the front or rear axle) equipped with electrification. The invention also relates to a partial electrification system specifically for the wheels.

[0002] The locking device involved in this situation, which involves mechanical engagement of a locking unit commonly referred to as the "parking brake," is typically used specifically in vehicles with automatic transmissions. This type of locking device is also used in electric or hybrid vehicles. The device for locking the transmission is activated when the driver positions the transmission selector lever in the "P" position (typically when the vehicle is stationary).

[0003] The locking device discussed in this context differs from and complements another braking system known as the parking brake (which also exists on motor vehicles and acts directly on the wheels of the vehicle). The parking brake also functions as an emergency brake for slowing down and stopping the vehicle. On the other hand, the parking brake, the subject of this invention, is configured and designed to engage only when the speed is zero or nearly zero.

[0004] Parking brake solutions are known in which a toothed pivoting element (pawl) selectively interacts with a toothed wheel that forms part of the transmission. However, known solutions occupy a corresponding amount of space (with a dedicated parking brake wheel), and furthermore, they are not without clearance. An example of this type of solution is known from document US2016223082.

[0005] The inventors attempted to improve this situation and proposed a new configuration for providing parking brake functionality, which is particularly compact, especially for electrified powertrains.

[0006] To this end, a transmission assembly for a motor vehicle is proposed, the assembly including means for locking via mechanical engagement of at least one locking unit, the assembly comprising at least:

[0007] - A spindle configured to rotate about a first axis and configured to be driven by a motor;

[0008] - The first pinion, which rotates integrally with the main shaft;

[0009] - A secondary shaft, which is assembled to rotate about a second axis, and is equipped with a second pinion and a third pinion with different numbers of teeth, the second pinion meshing with the first pinion;

[0010] - Output gear ring, which meshes with a third pinion, and the output gear ring is in a kinematic relationship with at least one wheel of the vehicle;

[0011] - A locking sleeve, which is centered on a first axis and can be axially displaced between an unlocked position and a locked position;

[0012] - A shift fork configured to shift a locking sleeve along a first axis between an unlocked position and a locked position, characterized in that, in the locked position, the locking sleeve directly rotatably connects the output gear ring to a first pinion or a main shaft, and the locking sleeve locks the rotation of the output gear ring due to a mutual subtraction ratio not equal to 1 between the first pinion and the output gear ring.

[0013] The feature “output gear ring is in a kinematic relationship with at least one wheel of the vehicle” specifically includes the following cases: direct engagement (sometimes using the term “electric wheel”) for the case of an electrified single wheel, or indirect engagement with two wheels via a differential (then using the term “electric axle”).

[0014] In this document, the term "meshing" refers to fixed mechanical meshing through complementary tooth profiles.

[0015] The term "locking sleeve" can also be referred to as "connecting sleeve," "forced clutch," or even "sliding shaft." This is an annular unit that includes an internal cannelure, as will be seen in more detail below. The locking sleeve forms the aforementioned locking unit.

[0016] Due to the arrangement described above, the parking brake function is located on the main axis, thus avoiding the need for a dedicated parking brake wheel (which is offset relative to the main axis). The proposed solution requires fewer parts to achieve this function than known prior art. Advantageously, the proposed system therefore eliminates the need for a dedicated parking brake wheel or any other related components.

[0017] The proposed configuration is compact and simple to manufacture and assemble. Advantageously, the proposed configuration is lighter than configurations known in the prior art.

[0018] It should be noted that in the unlocked position, the mechanical connection provided by the locking sleeve is no longer established between the output gear ring and the main shaft or the first pinion. According to one embodiment, the locking sleeve is then on the output gear ring side and rotates together with the output gear ring.

[0019] According to the alternative solution, the position when at rest can be on the other side, that is, on the side of the main shaft.

[0020] It should be noted that in this disclosure, the motor (which drives the main shaft) may be an electric motor, the rotor of which is rotatably connected to the main shaft. However, it is not excluded that the motor is an internal combustion engine, in which case the main shaft is driven directly or indirectly by the crankshaft of the engine, or via a clutch.

[0021] In one aspect, the output gear ring is connected directly or via a fixed gear (e.g., a reduction gear) to a single wheel of the vehicle. This provides a simple solution for a dedicated partial electrification system for the wheels. In vehicles with multiple partial wheel motorization systems, this type of parking brake function can be optionally equipped for one or more systems.

[0022] In one aspect, the output gear ring is connected to the two wheels of the vehicle via a differential comprising a gear ring and two planetary gears, wherein the output gear ring is formed by the differential gear ring. In this way, the transmission can be locked upstream of the differential, and parking brake function for both wheels of the vehicle axle is ensured using a single locking sleeve. This configuration is ideal for electrified axles, regardless of whether the axle is located at the front or rear of the vehicle.

[0023] In this context, it should be noted that the parking brake function is compatible with the differential lock function, and both functions can be implemented on the axle in question.

[0024] According to one aspect, the spindle is hollow and includes an axial through hole.

[0025] This hole allows an axle (also known as an axle half-shaft) to pass through, extending from the output of the differential to one of these wheels. In this way, the arrangement is completely coaxial, except for the countershaft.

[0026] According to one aspect, the differential has a first axial end portion (71) equipped with a first external rib structure that complements the internal rib structure of the locking sleeve and forms a position for the locking sleeve to be in a rest / unlocked position, wherein the first axial end portion rotates integrally with a portion supporting the differential ring gear, or the axial end portion forms part of the differential ring gear.

[0027] Due to the aforementioned ribbed structure, torque between the locking sleeve and the output gear ring can be eliminated. Typically, the ribbed structure preferably extends parallel to the first axis. The locking sleeve maintains at least partial overlap with the first axial end portion, particularly when the locking sleeve is in the locked position. In the unlocked position, the entire locking sleeve surrounds the first axial end portion, i.e., its resting position.

[0028] According to one aspect, the spindle may include a second axial end portion having a second external rib structure that can receive an internal rib structure of a locking sleeve.

[0029] Due to the aforementioned ribbed structure, torque between the locking sleeve and the spindle can be eliminated when the sleeve is in the locked position.

[0030] According to one aspect, the input chamfer is provided on the external rib structure of the second axial end portion on the mating side of the sleeve.

[0031] This facilitates the engagement of the sleeve on the spindle. An input chamfer can also be provided on the radially internal ribbed structure of the locking sleeve on one side of its front face for engagement.

[0032] According to one aspect, the first axial end portion (71) and the second axial end portion (52) are opposite to each other, face each other axially, and are spaced apart by a gap (E1) of less than 5 mm.

[0033] In order for the locking sleeve to meet and cover its target on one side of the spindle, the clearance to be passed through must be small enough.

[0034] According to one aspect, the first axial end portion and the second axial end portion have substantially the same outer diameter.

[0035] Therefore, the longitudinal ribbed structure of the locking sleeve can easily slide from the first axial end portion to cover the second axial end portion.

[0036] Depending on one aspect, the number of ribs can be between 20 and 40. This number minimizes the probability of difficulty in tooth-to-tooth meshing, while still maintaining a sufficiently large ribbed profile to withstand torque.

[0037] According to one aspect, the locking sleeve has an outer diameter (D1) and an axial dimension (L1), the outer diameter being less than 12 cm, preferably less than 10 cm, and the axial dimension being preferably less than 4 cm.

[0038] Therefore, the proposed solution is compact. The locking sleeve only bears torque at zero speed, and thus can have the most precisely calculated dimensions. This distinguishes the locking sleeve from differential lock-up clutches or gearboxes that must operate over a wide range of rotational speeds.

[0039] According to one aspect, the first pinion includes an external ribbed structure that can receive an internal ribbed structure of the locking sleeve. This is an alternative to the solution presented above, wherein the force-bearing ribbed structure is positioned on the main shaft. In this case, the ribbed structure is positioned on the main pinion.

[0040] According to one aspect, the input chamfer is set on the external rib structure of the first pinion on the mating side of the sleeve.

[0041] The present invention also relates to a drivetrain for a vehicle, the drivetrain including an electric motor and a transmission assembly as described above.

[0042] According to one aspect, the motor is an axial flow motor. According to another aspect, the motor is a radial flow motor.

[0043] The present invention also relates to an electrified axle for a vehicle, the electrified axle including a motor, two wheels, two axles connected to a differential, and a transmission assembly including the differential as described above.

[0044] The invention will be described in further detail by way of description of non-limiting embodiments and by way of the accompanying drawings illustrating variations thereof, in which:

[0045] -[ Figure 1 An example of a transmission assembly according to the invention is shown schematically in cross-section, wherein the locking sleeve is in the unlocked position;

[0046] -[ Figure 2 [Shown schematically in cross-section] Figure 1 The transmission assembly in which the locking sleeve is in the locked position;

[0047] -[ Figure 3 Another example of a transmission assembly according to the invention is shown schematically in cross-section;

[0048] -[ Figure 4 Another example of a transmission assembly according to the invention is shown schematically in cross-section;

[0049] -[ Figure 5 The area of ​​the locking sleeve is schematically shown in cross-section;

[0050] -[ Figure 6 A three-dimensional illustration of a locking sleeve is provided.

[0051] -[ Figure 7 The cross-sectional view shows the details of the meshing of the ribbed structure.

[0052] In different accompanying drawings, the same reference numerals designate the same or similar elements. For clarity of description, some elements are not necessarily shown to scale.

[0053] Figure 1 and Figure 2 This illustrates an embodiment of an electrified axle. The axle may form part of the front axle of a vehicle or part of the rear axle of a motor vehicle. The axle may be an axle with drive wheels or non-drive wheels. Typically, an electrified axle includes a motor unit, a transmission (which includes a differential), two axles, and two wheels. The transmission may include reduction gears, which, if applicable, have multiple selectable reduction ratios (i.e., a gearbox); and optionally, as will be seen below, the transmission may include means for connecting two rotating elements together.

[0054] More specifically, this type of axle includes a left wheel and a right wheel, not shown in the accompanying drawings. As is known, a differential 7 is located in the middle portion of the axle. The first output of the differential is integrally rotatably connected to the left axle ARG, which itself is rotatably connected to the left wheel. The other output of the differential is integrally rotatably connected to the right axle ARD, which itself is rotatably connected to the right wheel.

[0055] Differential 7 allows for different wheel speeds, particularly when the vehicle is cornering, or when one wheel slips or slides. A device (not shown in the figures) may be provided for locking the differential, which, at certain stages of the vehicle's life, allows one of the output shafts to rotate integrally with the differential body.

[0056] The two axles, ARG and ARD, rotate around the first axis as indicated by A1. The differential body 70 also rotates around axis A1.

[0057] In the example shown, the axle is motorized by an electric motor, labeled 6 in the attached figure. The axis of the electric motor coincides with the first axis A1.

[0058] In the example shown, the rotor 60 is flat and the magnetic flux is axial. In an alternative example, the motor could be a motor with radial magnetic flux. It is not excluded that the axis of the electric motor differs from the first axis.

[0059] It should be noted that the housing / bridge housing is not shown in the attached drawings, and only symbolic representation is shown of assembly and guidance via bearings.

[0060] Rotor 60 is mounted on a shaft referred to as main shaft 5. The main shaft is hollow and includes an axial through-hole, indicated by reference numeral 50. Left wheel axle ARG is housed within the bore 50 of the main shaft 5. The left wheel axle ARG and main shaft 5 are coaxial. A small functional clearance is provided to allow the axle to rotate within the bore 50 of the main shaft. The left wheel axle ARG is connected to the conical output pinion 77 of the differential 7.

[0061] The first pinion, denoted by reference numeral 21, is positioned on the main shaft 5. The first pinion may be integrally formed with the main shaft, or it may be an additional part integrally rotatably mounted on the main shaft 5. The main shaft 5 may include a shoulder, a seat, an annular channel for a resilient retaining ring, a keyway, and any other means or functions known per se.

[0062] The torque generated by the electric motor 6 is supplied downstream via the first pinion 21 (particularly via the outer teeth of the first pinion).

[0063] The spindle has an end on the differential side, the purpose of which will be described below.

[0064] In addition to the differential, the transmission assembly also includes a countershaft 2. The countershaft is assembled to rotate about a second axis as indicated by A2. The second axis A2 is spaced apart from the first axis A1 by a distance typically between 10 cm and 20 cm.

[0065] The countershaft 2 is equipped with a second pinion 22 and a third pinion 23. The second pinion 22 and the third pinion 23 have different numbers of teeth. The second pinion 22 meshes with the first pinion 21.

[0066] The countershaft can be integrally manufactured with the second and third pinions (all three). Alternatively, one of the pinions can be an additional part, which is fitted onto the ribbed structure, either by means of a key or pin, or by means of a smooth interference fit. The two pinions 22 and 23 can be additional parts rigidly mounted on the shaft.

[0067] The secondary shaft 2 can be hollow or solid. In relation to the main shaft, the secondary shaft may include a shoulder, a seat, an annular channel for a resilient retaining ring, a keyway, and any other means or functions known per se.

[0068] The differential 7 includes an external gear ring with toothed teeth. In this document, this external gear ring is also referred to as the "output gear ring" and is denoted as 3 in the figure. The output gear ring 3 is centered on axis A1 and coaxial with the main shaft 5.

[0069] The third pinion 23 meshes with the output gear ring 3. Due to the cascading of the two reductions, the output gear ring rotates slower than the main shaft; that is, the first reduction is achieved by the second pinion meshing with the first pinion, followed by the reduction achieved by connecting the output gear ring with the third pinion.

[0070] According to Figure 1 and Figure 2In the configuration with a differential shown, the ring gear of the differential 3 drives the axle 75 of the planetary gears, while the conical planetary gears 76 in turn drive the conical pinions 77 connected to the axles of the corresponding wheels. Since the differential itself is considered known, it will not be described further.

[0071] Advantageously, according to the present invention, a locking sleeve 1 is provided.

[0072] The body of the differential 70 includes a ribbed seat 71 for receiving the locking sleeve 1 around the ribbed seat. The ribbed seat 71 is referred to herein as a first axial end portion. The ribbed seat 71 includes a ribbed structure, referred to herein as a first external ribbed structure 73, which receives a radially internal ribbed structure of the locking sleeve.

[0073] The locking sleeve 1 can also be referred to as a connecting sleeve, a forced clutch, a claw-shaped structure, or a sliding shaft. This is an annular unit comprising internal shaped components, including ribbed structures 12 oriented longitudinally relative to a first axis, and... Figure 6 and Figure 7 As shown in the image.

[0074] Furthermore, the locking sleeve 1 includes an annular channel 10 that opens to the outside. This annular channel is defined by two edges 16.

[0075] At least one free end of the shift fork 4 engages in the annular channel 10. Preferably, the shift fork 4 has a semi-circular shape, engaging in the channel within an annular range of approximately 180°. Alternatively, two diametrically opposed finger-shaped members may be present in the shift fork.

[0076] Locking sleeve 1 is centered on the first axis A1. Locking sleeve 1 can be axially displaced between an unlocked position, referred to as P1, and a locked position, referred to as P2.

[0077] The shift fork 4 can be moved along axis A1 so that the locking sleeve is along the first axis A1. Figure 1 The unlock position P1 indicated is related to the Figure 2 The indicated locking positions P2 are shifted.

[0078] The shift fork 4 can be translated along the first axis. Alternatively, the shift fork 4 can be configured to rotate and pivot relative to an auxiliary axis that is spaced apart from and perpendicular to the first axis.

[0079] The shift fork 4 does not rotate about the first axis A1, but the locking sleeve 1 rotates about axis A1 normally when the vehicle moves. In the unlocked position (stationary state), the locking sleeve can be in the rotated position, and the end of the shift fork can slide without contact in the annular channel 10.

[0080] In the locked position, the locking sleeve 1 directly rotatably connects the output gear ring 3 to the main shaft 5. In other words, the locking sleeve 1 directly and integrally rotatably connects the output gear ring 3 and the main shaft 5, and therefore the locking sleeve limits... 5 = 3. 5 is the spindle rotation speed. 3 is the rotational speed of the differential body.

[0081] In addition, due to the meshing of the pinions, there is a meshing ratio. 3 = K x 5, where K is not equal to 1, because of the cascading of the tooth difference between the first pinion 21 and the second pinion 22, and the tooth difference between the third pinion 23 and the output gear ring 3. In practice, K is much less than 1 (a considerable level of deceleration).

[0082] The only solution for this statically indeterminate system is 5 = 0 and 3 = 0, meaning locked.

[0083] Therefore, due to the meshing of the pinions in a cascaded manner with a reduction ratio not equal to 1, the engagement of the locking sleeve causes the differential's ring gear to lock in rotation.

[0084] Preferably, the command to shift the shift fork 4 to the left (i.e., to the coupling position) is only authorized when the vehicle speed is zero, or optionally almost zero (i.e., below 3 km / h).

[0085] The control unit (not shown in the attached diagram) is responsible for the logic of controlling the position of the locking sleeve based on whether the gear lever is in the "P" position or not, and based on the current speed of the vehicle.

[0086] It can be noted that the locking sleeve only bears torque at zero speed; that is, the locking sleeve never bears torque when rotating. This allows for the calculation of the locking sleeve's diameter D1 and the dimensions of its ribbed structure 12 with the greatest possible precision. Comparing this locking sleeve to the sliding shaft of a gearbox or the locking sleeve of a differential also allows for more lenient material selection or the omission of certain heat treatments.

[0087] The ribbed structure 12 of the locking sleeve has a clearly defined input chamfer 14, wherein the end of the ribbed structure is in the form of a pointed tip. The input chamfer 14 is specifically provided on the side of the front end face 17 of the sleeve that advances during translation toward the locking position. Therefore, at the moment of engagement, even in the unfavorable situation where the ribbed structure assemblies face each other, the pointed tip form of the ribbed structure 12 can engage with the ribbed structure 54 on the spindle side by a small rotation (if applicable).

[0088] The spindle 5 includes a second axial end portion 52 with a ribbed structure 54, the ribbed structure of the second axial end portion being capable of receiving a radially internal ribbed structure 12 of the locking sleeve.

[0089] The ribbed structure 54 on one side of the spindle 5 also has an input chamfer 55.

[0090] The number of ribs 12 can be between 20 and 40. It should be understood that the number of ribs selected for forming the concave portion of the locking sleeve is the same as the number of ribs selected for the two convex portions that are positioned end-to-end and are at least partially covered by the locking sleeve.

[0091] The inner diameter D3 of the locking sleeve is slightly larger than the diameter of the main shaft excluding the ribbed structure.

[0092] The outer diameter D5 of the wheel axle is smaller than the diameter D4 of the hole 50 set in the main shaft.

[0093] The locking sleeve 1 has an axial dimension L1, which is preferably less than 4 cm. The outer diameter D1 is less than 12 cm and preferably less than 10 cm. Depending on the torque specification, the diameter D1 can be even smaller. In one embodiment, L1+D1 can be selected to be less than 14 cm.

[0094] As in Figure 5 As can be seen, the first axial end portion 71 and the second axial end portion 52 are opposite to each other, that is, the first axial end portion and the second axial end portion face each other and are spaced apart by a gap E1 of less than 5 mm. In some embodiments, the gap E1 is less than 4 mm, or even less than 3 mm.

[0095] The first axial end portion 71 and the second axial end portion 52 have substantially the same outer diameter D2.

[0096] It can be noted that the components used (including the locking sleeve 1) are lubricated by the transmission oil through splash lubrication.

[0097] according to Figure 3 In the second embodiment presented, the connecting sleeve 1 directly covers part 25 of the first pinion, rather than covering part of the main shaft. However, since the first pinion 21 is coaxial with the main shaft 5 and integrally rotatably connected to the main shaft, the function of the first pinion is the same as that described above for the first embodiment.

[0098] The so-called second axial end portion is then located on the first pinion 21.

[0099] Therefore, since the outer diameter of the second axial end portion of the first pinion is known to be substantially the same as the outer diameter D2 of the first axial end portion 71, a smaller diameter spindle 5 can be realized.

[0100] according to Figure 4 The third embodiment shown in the diagram does not have a differential because the system involves only one wheel and there is only a single output shaft AR facing the wheel. The gear ring 3 that meshes with the third pinion 23 is the gear ring of a conventional gear (which may be referred to herein as the fourth pinion 44) that is rotatably connected to the wheel axle AR.

[0101] Similar to the arrangement described above for the differential body, the fourth pinion 44 of the third embodiment includes a seat for receiving a ribbed locking sleeve, the seat forming a first axial end portion 71.

[0102] Therefore, it should be understood that the term "output gear ring" refers to the gear ring of the differential body, or to the peripheral portion of the conventional pinion.

[0103] In other words, the output gear ring 3 is configured to be kinematically connected to at least one wheel of the vehicle. In the third embodiment, the feature "kinematically connected to at least one wheel of the vehicle" means direct engagement for the case of an electrified single wheel. In the first embodiment, the feature "kinematically connected to at least one wheel of the vehicle" means indirect engagement with two wheels via the differential 7.

[0104] All parts of the transmission assembly are made of metal, particularly steel or cast iron. The parts of the transmission assembly are lubricated by splash lubrication of oil present in the base of the housing, or by forced lubrication by means of an oil pump.

[0105] It can be noted that in the configuration recommended here, the following parts are coaxially assembled with respect to the first axis A1: main shaft 5, first pinion 21, output gear ring 3, locking sleeve 1, and wheel axle AR or wheel axle ARG, ARD.

[0106] It can be noted that the parking brake function proposed here does not require friction elements; nor is there a synchronizer associated with the locking sleeve.

Claims

1. A transmission assembly for a motor vehicle, the assembly including means for locking via mechanical engagement of at least one locking unit, the assembly comprising at least: - A spindle (5) configured to rotate about a first axis (A1) and configured to be driven by a motor; - First pinion (21), which rotates integrally with the main shaft; - A secondary shaft (2) is assembled to rotate about a second axis (A2), the secondary shaft being equipped with a second pinion (22) and a third pinion (23) having different numbers of teeth, the second pinion (22) meshing with the first pinion (21); - Output gear ring (3), which meshes with the third pinion (23), the output gear ring being configured to be in a kinematic relationship with at least one wheel of the vehicle; - A locking sleeve (1) that is centered on the first axis and is axially displaceable between an unlocked position (P1) and a locked position (P2); - A shift fork (4) configured to shift the locking sleeve along the first axis between the unlocked position (P1) and the locked position (P2), characterized in that, in the locked position, the locking sleeve directly rotatably connects the output gear ring (3) to the first pinion (21) or the main shaft (5), and the locking sleeve locks the rotation of the output gear ring due to the meshing of the first pinion and the output gear ring with a mutual reduction ratio not equal to 1.

2. The transmission assembly as claimed in claim 1, wherein, The output gear ring is connected directly to a single wheel of the vehicle, or via a fixed gear to a single wheel of the vehicle.

3. The transmission assembly as claimed in claim 1, wherein, The output gear ring is connected to the two wheels of the vehicle via a differential (7), which includes a gear ring and two planetary gears, wherein the output gear ring is formed by the differential gear ring (3).

4. The transmission assembly as described in claim 3, wherein, The spindle (5) is hollow and includes an axial through hole (50).

5. The transmission assembly as described in any one of claims 3 and 4, wherein, The differential has a first axial end portion (71) equipped with a first external rib structure (73) that complements the internal rib structure (12) of the locking sleeve and forms a position for the unlocking position of the locking sleeve, wherein the first axial end portion rotates integrally with the differential ring gear, or the axial end portion forms part of the differential ring gear.

6. The transmission assembly as claimed in any one of claims 1 to 5, wherein, The spindle (5) includes a second axial end portion (52) having a first external rib structure capable of receiving the internal rib structure of the locking sleeve.

7. The transmission assembly as described in claims 5 and 6, wherein, The first axial end portion (71) and the second axial end portion (52) are opposite to each other, facing each other axially, and are spaced apart by a gap (E1) of less than 5 mm.

8. The transmission assembly as claimed in any one of claims 1 to 5, wherein, The locking sleeve has an outer diameter (D1) and an axial dimension (L1), the outer diameter being less than 12 cm.

9. The transmission assembly as claimed in any one of claims 1 to 5, wherein, The first pinion (21) includes an external ribbed structure that can receive the internal ribbed structure (12) of the locking sleeve.

10. A drivetrain for a vehicle, the drivetrain comprising an electric motor and a transmission assembly as claimed in any one of claims 1 to 9.

Images