Limited-slip differential module

Abstract

The invention relates to a differential module comprising: a housing (9) receiving torque supplied by a traction motor; at least one planetary gear (11) pivotally mounted on the housing (9); first and second planetary gears (12, 13) meshing with the at least one planetary gear and rotating a first and second wheel drive half-shaft (3, 4); and a clutch (14) configured to transmit and interrupt the passage of a portion of the torque from the housing to the second wheel drive half-shaft (4), the clutch cooperating with a torque input element and a torque output element; characterized in that the torque input element is supported by a radially external surface of the housing. (Abstract figure: 2a)

Description

Title of the invention: Limited-slip differential module technical field

[0001] The present invention relates to a differential module of a transmission system for a vehicle, and more particularly to a differential module comprising a clutch offering limited slip and locking capabilities. Technological background

[0002] Differentials are installed on vehicles to allow an outer drive wheel to rotate faster than an inner drive wheel when cornering, while both drive wheels continue to receive power from the engine. Although differentials are useful when cornering, they can cause the vehicle to lose traction, for example, in snow, mud, or other slippery surfaces. If one of the drive wheels loses traction, it will rotate at a high speed while the other wheel may not rotate at all.

[0003] To remedy this situation, limited-slip differentials have been developed to transfer power from the drive wheel that has lost traction and tends to run away to the drive wheel that is not turning.

[0004] A limited-slip differential device for transmitting and distributing torque from an engine to two half-shafts of a vehicle axle is known, notably from US patent 6561939. The device comprises a housing driven by a traction motor and containing two satellite gears that mesh with two planetary gears. Each planetary gear is configured to drive one half-shaft of the vehicle axle. A multi-disc clutch controlled by an actuation system is provided to selectively engage the housing with a wheel half-shaft, for example, when a wheel loses traction.Half of the friction discs of the multi-disc clutch have external teeth that cooperate in rotation with an external disc carrier fixed rigidly to the housing, and the other half of the friction discs of the multi-disc clutch have internal teeth that cooperate in rotation with a splined sleeve linked in rotation to a wheel drive half-shaft.

[0005] Such a limited-slip differential device structure presents several technical problems, primarily its insufficient compactness. Indeed, the design of such a structure necessitates the axial superposition of the differential housing, the clutch, and the actuation system. This therefore implies a The overall size is significant in the axial direction, which can prove incompatible with the very limited space available in modern transmissions, particularly those for electric vehicles. Alongside improved compactness, the limited-slip differential mechanism must be simpler and more economical to manufacture. Summary

[0006] In all that follows, ordinal numeral adjectives are used to differentiate features. They do not define the position of a feature. Therefore, for example, a third feature of a product does not mean that the product has a first and / or a second feature.

[0007] An idea underlying the invention is a limited-slip differential module that makes it possible to solve one or more technical problems of the prior art, for example the aforementioned problems.

[0008] The invention relates to a differential module for a vehicle transmission system, the differential module having a first axis of rotation and comprising: • a housing receiving a torque supplied, directly or indirectly, by a traction motor; • at least one satellite gear mounted on the housing and pivoting around a second axis of rotation; • a first and a second planetary gear pivoting around the first axis of rotation and meshing with at least one satellite gear, the first and second planetary gears respectively driving a first and a second half-shaft of the wheel drive; and • a clutch configured to transmit and interrupt a passage of at least a portion of the torque from the housing to the second wheel drive half-shaft or from the housing to the second planetary gear, the clutch cooperating with a torque input element and a torque output element; the input element of the torque being supported by a radially external surface of the housing.

[0009] Thanks to the architecture according to the invention, the housing supports both at least one planetary gear and the torque input element. This makes it possible to perform these two support functions with a single component, which constitutes an economical and radially compact solution.

[0010] For the purposes of this application: • “axially” means “parallel to the first axis of rotation”; • “Radially” means “along an axis belonging to an orthogonal plane” to the first axis of rotation and cutting across this first axis of rotation"; • The terms "external" and "internal" are used to define the relative position of a component with respect to the axis of rotation for which it is concentric; a component close to said axis is thus described as internal as opposed to an external component located radially on the periphery; • “Rotationally linked” means “assembled in such a way that one does not rotate by "relative to the other." In other words, it is a fixed connection in rotation, possibly exhibiting very little play such as spline play; • Two parts are said to be "fixed" when they are permanently immobilized relative to each other, this immobilization being able to result from the first part being fixed to the second part directly or through one or more intermediate parts.

[0011] According to one aspect of the invention, the torque input element supported by the radially external surface of the housing is formed as a single piece with the housing, the torque input element being obtained in particular by a process of removing or deforming material from the housing

[0012] According to another aspect of the invention, the torque input element supported by the radially external surface of the housing is an added part fixed to the housing, in particular fixed by welding, shrink fitting, screwing, riveting or crimping.

[0013] According to an additional feature of the invention, the clutch axially covers at least one satellite gear.

[0014] According to a further feature of the invention, the clutch is positioned axially so that it is crossed by a plane perpendicular to the first axis of rotation and passing through the second axis of rotation.

[0015] Thanks to these last two features, the clutch can have an axially recentred position relative to the differential gears, which makes it possible to reduce the axial dimension of the housing required to support both at least one satellite gear and the torque input element.

[0016] Moreover, thus positioned, the clutch is located on a large diameter, which gives it an increased torque capacity.

[0017] According to a further feature of the invention, the torque output element is carried by a rotating support around the first axis of rotation, the rotating support having at least one radially internal surface surrounding the housing radially, the radially internal surface being spaced from the housing by a radial clearance.

[0018] Thus defined, the shape of the rotating support combined with the shape of the housing advantageously allows for the creation of a radial space for housing the clutch. The play The radial design prevents any contact between the housing and the rotating support, as these two parts can rotate at different speeds.

[0019] According to one aspect of the invention, the torque output element carried by the rotating support is made as a single unit with the rotating support, the torque output element being obtained in particular by a process of removing or deforming material from the rotating support.

[0020] According to another aspect of the invention, the torque output element carried by the rotating support is an added part fixed to the rotating support, in particular fixed by welding, shrink fitting, screwing, riveting or crimping.

[0021] This last feature can simplify manufacturing by choosing an appropriate manufacturing process for each part of the rotating support. For example, the torque output element can be made by a stamping process and the rotating support by a forging process.

[0022] According to an additional feature of the invention, the rotating support is rotationally linked to the second half-shaft of the wheel drive or to the second planetary pinion, in particular by a spline.

[0023] Thanks to this feature, the transmission of torque from the torque output element to the second wheel drive half-shaft can be ensured directly. The use of a spline simplifies assembly by allowing the rotating support to be inserted into the second wheel drive half-shaft.

[0024] According to a further feature of the invention, the rotating support and the housing are radially centered with respect to each other by at least one first bearing.

[0025] Thus, the rotating support and the housing can support each other despite the fact that these two components can potentially rotate at different rotational speeds.

[0026] According to a further feature of the invention, the rotating support is able to be supported by a transmission housing via at least one second bearing, and the housing is able to be supported by the transmission housing via at least one third bearing.

[0027] Thanks to the structure described by this last characteristic, the rotational coaxiality of the different components of the differential module and the transfer of forces by the transmission housing are ensured.

[0028] According to a further feature of the invention, the clutch is actuated by an actuation system, the actuation system being supported by the rotating support via a fourth bearing.

[0029] This feature allows in particular that the actuation system can be integrated into the sub-assembly constituted by the differential module.

[0030] According to a further feature of the invention, the clutch comprises a plurality of stacked friction discs.

[0031] The plurality of friction discs allows the transmission of a high level of torque when the clutch is completely closed, as well as easy modulation of the level of torque transmitted according to the conditions of use of the vehicle thanks to the possibility of sliding the discs against each other.

[0032] According to an additional feature of the invention: • the input element of the couple forms a first external toothing, and the output element of the couple forms a first internal toothing; • A first set of friction discs has a second external toothing, and a second set of friction discs has a second internal toothing; and • the first external dentition cooperating with the second internal dentition and the first internal dentition cooperating with the second external dentition.

[0033] According to a further feature of the invention, the actuation system includes a movable support means configured to exert pressure on the friction discs, said movable support means passing through openings provided in the rotating support.

[0034] This feature allows the actuation system to be integrated on the rotating support in a compact manner.

[0035] The differential module according to the invention may have one or more of the characteristics described below, either combined or taken independently of each other: • at least one satellite gear and both planetary gears can be bevel gears; • at least one satellite gear is pivotally mounted on a cylindrical rod fixed to the housing; • the number of satellite gears is between one and twelve, in particular four; • at least one satellite pinion and the two planetary pinions can be made in the form of cylindrical gears, in particular straight-toothed gears, in particular gears arranged in the form of an epicyclic train; • the housing has an internal cavity in which are housed at least one satellite gear and the two planetary gears; • the two planetary gears are supported by the housing; • the casing can be made in several parts, fixed together by a means of fastening, in particular by welding or by screwing or by riveting; • a toothed wheel is fixed to the housing, the toothed wheel receiving, via a set of gears, the torque supplied by the traction motor; • the first, second, third and fourth bearings can be plain bearings or ball bearings or roller bearings or a sliding coating; • a first axial bearing, in particular formed by an axial needle thrust bearing or a smooth axial bearing, is interposed axially between the housing and the rotating support; • the clutch can be of the friction clutch type or viscous coupling clutch or dog clutch type; • the actuation system can be mechanical, electromechanical, electromagnetic, pneumatic or hydraulic; • the actuation system may include a ball ramp;

[0036] The invention further relates to a torque transmission system, particularly for automobiles, comprising a differential module as defined above and further comprising: • a set of gears capable of cooperating kinematically in rotation with, on the one hand, a traction motor and, on the other hand, with the differential module to form one or more speed reduction ratios; • a transmission casing in which the gear set and differential module are housed.

[0037] The invention further relates to a powertrain comprising a traction motor and a torque transmission system as defined above. Brief description of the figures

[0038] [Fig-1] Fig. 1 illustrates a schematic cross-sectional view of a powertrain including a differential module according to the invention.

[0039] [Fig.2a] The [Fig.2a] is a cross-sectional view of the differential module according to the invention.

[0040] [Fig.2b] [Fig.2b] is a detail view of [Fig.2a].

[0041] [Fig.2c] The [Fig.2c] is another detailed view of the [Fig.2a].

[0042] [Fig.3] The [Fig.3] is a cutaway perspective view of the differential module according to the invention.

[0043] [Fig.4] The [Fig.4] is a perspective view of the differential module housing according to the invention.

[0044] [Fig.5] The [Fig.5] is a cutaway perspective view of the rotating support of the differential module according to the invention.

[0045] [Fig.6] The [Fig.6] is a perspective view of the friction discs of the clutch of the differential module according to the invention. Description of the implementation methods

[0046] In all the figures, identical elements or elements performing the same function are identified by the same reference numerals. The following embodiments are examples. Although the description refers to one or more embodiments, this does not necessarily mean that each reference numeral relates to the same embodiment or that the features apply only to a single embodiment. Simple features from different embodiments can also be combined or interchanged to provide other embodiments.

[0047] Figure 1 schematically illustrates a powertrain 1 according to an embodiment of the invention. The powertrain 1 comprises a differential module 2 for rotating two wheel drive half-shafts 3 and 4 of a vehicle axle and configured to distribute torque from a traction motor 5 to the wheel drive half-shafts 3 and 4, allowing them to rotate at different speeds.

[0048] Such a differential module 2 is for example intended for a hybrid vehicle. Thus, powertrain 1, for example, is capable of transmitting torque from an electric motor to a rear or front axle of the vehicle, while another powertrain coupled to a different engine, such as an internal combustion engine, generates torque and transmits it between that other engine and the half-shafts of the wheels 3,4 on the other axle of the vehicle. Another powertrain configuration for a hybrid vehicle might consist of a combination of an internal combustion engine and an electric motor, both working together to transmit torque to the half-shafts of the wheels 3,4 on the same axle. The vehicle could also be fully electric.

[0049] As shown in [Fig. 1], the powertrain 1 comprises a transmission housing 6 in which a traction motor 5, a differential module 2, and a gear set 7 are housed. The structure of the transmission housing 6 may be a single unit or composed of several sub-parts. The traction motor 5 includes, at its output, a shaft rotating about a third axis of rotation X3. The gear set 7 cooperates kinematically in rotation with, on the one hand, the shaft of the traction motor 5 and, on the other hand, with the differential module 2 to form one or more speed reduction ratios.

[0050] In the non-limiting example of [Fig. 1], the gear set 7 comprises a first set of cylindrical gears 701, coaxial with the third axis of rotation X3, and cooperating kinematically in rotation with a second set of cylindrical gears 702, coaxial with a fourth axis of rotation X4 parallel to the third axis of rotation X3, to form a first reduction ratio. The second set cylindrical gears 702 cooperate kinematically in rotation with a toothed wheel 8 attached to a housing 9 of the differential module 2 to form a second reduction ratio.

[0051] In this example, the traction motor 5 can be an electric or internal combustion engine. Another electric or internal combustion engine (not shown) can also be coupled with one of the gears in the gear set 7.

[0052] Figures 2a, 2b and 3 illustrate the differential module 2 having a first axis of rotation XI and comprising a housing 9 receiving, via the gear 8, torque supplied by the traction motor 5, two planetary gears 11 mounted on the housing 9 and pivoting about a second axis of rotation X2, a first and a second planetary gear 12, 13 pivoting about the first axis of rotation XI and meshing with the two planetary gears 11, the first and second planetary gears 12, 13 respectively driving a first and a second wheel drive half-shaft 3, 4 and a clutch 14 configured to transmit and interrupt the passage of at least a portion of the torque from the housing 9 to the second wheel drive half-shaft 4 or from the housing 9 to the second planetary gear 13, the clutch 14 comprising a torque input element 901 and a output element of couple 1501,the input element of the couple 901 being supported by a radially external surface 905 of the housing 9.

[0053] In this embodiment, the housing 9 can form a cavity that houses and supports the planetary gears 11 and the planetary gears 12, 13. The planetary gears 11 and the planetary gears 12, 13 are bevel gears. A cylindrical rod 902 can be fixed to the housing 9, the planetary gears 11 being pivotally mounted about the second axis of rotation X2 on said cylindrical rod 902. There can be one to four planetary gears 11, choosing four having the advantage of being able to transmit the torque with smaller planetary gears. The second axis of rotation X2 is perpendicular to the first axis of rotation XL. The housing 9 can be made in two parts 9a and 9b to allow easy assembly of the satellite gears 11 and planetary gears 12,13 inside the housing 9, the two parts 9a,9b of the housing 9 being welded together after this assembly.The planetary gears 12, 13 are mounted and rotationally connected to the two half-shafts of the wheel drive 3, 4 via splines 301, 401. Two friction washers 16, 17 are inserted axially between the two planetary gears 12, 13 and the housing 9 to limit wear and friction generated by the relative movement of the parts. The gear 8 can be fixed to the housing 9 by fixing screws 801.

[0054] The differential module 2 described above corresponds to a differential design in its most common form. According to another embodiment of the invention not shown, the differential may be of the "flat differential" type where the Satellite gears and planetary gears are made in the form of cylindrical gears, in particular straight-toothed gears, in particular gears arranged in the form of an epicyclic train.

[0055] The clutch 14 can axially cover the satellite gears 11. The clutch 14 can be positioned axially so that it is crossed by a plane perpendicular to the first axis of rotation XI and passing through the second axis of rotation X2.

[0056] The output element of the torque 1501 can be carried by a rotating support 15 around the first axis of rotation XL. The rotating support 15 can have a radially internal surface 1502 surrounding radially the housing 9. A radial clearance J is provided between the housing 9 and the rotating support 15 in order to avoid any direct contact between these two parts which can rotate at different speeds.

[0057] The rotating support 15 can be rotationally linked to the second half-shaft of the wheel drive 4 by a spline 1503.

[0058] The rotating support 15 and the housing 9 can be radially centered relative to each other by a first bearing 18, here a plain radial bearing. The rotating support 15 can be supported by the transmission housing 6 via a second bearing 19, here a ball bearing. The housing 9 can be supported by the transmission housing 6 via a third bearing 20, here a ball bearing. An additional radial centering 903 can be provided between the housing 9 and a wheel drive half-shaft 3,4. Furthermore, a first plain axial bearing 21 can be inserted between the rotating support 15 and the housing 9 in order to adjust the relative axial positioning and reduce friction between these two parts.

[0059] The clutch 14 is actuated by an actuation system 22. The actuation system 22 can be supported by the rotating support 15 via a fourth bearing 23, here a ball bearing. The actuation system 22 can be configured to axially move a movable support means 2201 from the engaged position to the disengaged position of the clutch 14. In all the figures, the actuation system is shown in the disengaged position. In the engaged position, the movable support means 2201 exerts axial pressure on the friction discs 1401 of the clutch 14, said movable support means 2201 passing through openings 1504 (visible in [Fig. 5]) provided in the rotating support 15.

[0060] The actuation system 22 can be mechanical, electromechanical, electromagnetic, pneumatic, or hydraulic. As illustrated in [Fig. 2c], the actuation system 22 can be formed by a ball ramp comprising a first ramp 2202 and a second ramp 2203. A ring 2204 between the first ramp 2202 and the second ramp 2203 retains balls 2205. The first ramp 2202 is configured to be driven in rotation around the The first axis of rotation XI is driven directly or indirectly by an actuator motor (not shown). The second ramp 2203 is prevented from rotating by the transmission housing 6 and is configured for axial translation. The second ramp 2203 is connected to the movable support 2201 via a second axial bearing 2206, here a needle thrust bearing. The ramps 2202 and 2203 have shapes adapted so that, when rotated relative to each other by the actuator motor, these ramps allow the movable support 2201 to be moved axially.

[0061] As illustrated in [Fig.4], the input element of the couple 901 can be made as a single piece with the housing 9. Here, the input element of the couple 901 is made in the form of a first external toothing, for example obtained by machining the housing 9.

[0062] Similarly, as illustrated in [Fig.5], the output element of the torque 1501 can be made as a single piece with the rotating support 15. Here, the output element of the torque 1501 is made in the form of a second internal toothing, for example obtained by stamping the rotating support 15.

[0063] As illustrated in [Fig. 6], the clutch 14 may comprise a plurality of stacked friction discs 1401. This plurality of friction discs may be radially positioned between the housing 9 and the rotating support 15. The plurality of friction discs 1401 consists of a first set of friction discs 1403 having a second external toothing 1405 cooperating with the torque output element 1501 formed by the first internal toothing of the rotating support 15, and a second set of friction discs 1402 having a second internal toothing 1406 cooperating with the torque input element 901 formed by the first external toothing of the housing 9. The discs of the first set 1403 and the second set 1402 are arranged alternately so as to obtain a multitude of friction surfaces.

[0064] It is emphasized that all features, as they are apparent to a person skilled in the art from the present description, drawings and attached claims, even if in practice they have only been described in relation to other specific features, both individually and in any combinations, can be combined with other features or groups of features disclosed herein, provided that this has not been expressly excluded or that technical circumstances make such combinations impossible or meaningless.

[0065] The use of the verb "comporter", "comprendre" and its conjugated forms does not exclude the presence of other elements or other steps than those stated in a claim.

[0066] In the claims, any reference sign in parentheses shall not be interpreted as a limitation of the claim.

Claims

Demands

1. Differential module (2) for a vehicle transmission system, the differential module (2) having a first axis of rotation (XI) and comprising: • a housing (9) receiving torque supplied, directly or indirectly, by a traction motor (5); • at least one satellite pinion (11) mounted on the housing (9) and pivoting about a second axis of rotation (X2); • a first and a second planetary pinion (12,13) ​​pivoting about the first axis of rotation (XI) and meshing with the at least one satellite pinion (11), the first and second planetary pinions (12,13) ​​respectively driving in rotation a first and a second wheel drive half-shaft (3,4);and • a clutch (14) configured to transmit and interrupt a passage of at least a portion of the torque from the housing (9) to the second wheel drive half-shaft (4) or from the housing (9) to the second planetary gear (13), the clutch (14) cooperating with a torque input element (901) and a torque output element (1501), the torque input element (901) being supported by a radially external surface (905) of the housing (9); characterized in that the clutch (14) is axially positioned so that it is traversed by a plane perpendicular to the first axis of rotation (XI) and passing through the second axis of rotation (X2).

2. Differential module (2) according to claim 1, wherein the clutch (14) axially covers at least one satellite pinion (H).

3. Differential module (2) according to any one of the preceding claims, wherein the torque output element (1501) is carried by a rotating support (15) about the first axis of rotation (XI), the rotating support (15) having at least one radially internal surface (1502) radially surrounding the housing (9), the radially internal surface (1502) being spaced from the housing (9) by a radial clearance (J).

4. Differential module (2) according to claim 3, wherein the rotating support (15) is rotationally linked to the second wheel drive half-shaft (4) or to the second planetary pinion (13), in particular by a spline (1503).

5. Differential module (2) according to claim 3 or 4, wherein the rotating support (15) and the housing (9) are radially centered with respect to each other by at least one first bearing (18).

6. Differential module (2) according to any one of claims 3 to 5, wherein the rotating support (15) is able to be supported by a transmission housing (6) via at least one second bearing (19), and the housing (9) is able to be supported by the transmission housing (6) via at least one third bearing (20).

7. Differential module (2) according to any one of claims 3 to 6, wherein the clutch (14) is actuated by an actuation system (22), the actuation system (22) being supported by the rotating support (15) via a fourth bearing (23).

8. Differential module (2) according to any one of the preceding claims, wherein the clutch (14) comprises a plurality of stacked friction discs (1401).

9. Differential module (2) according to claim 8, wherein: • the input element of the torque (901) forms a first external toothing, and the output element of the torque (1501) forms a first internal toothing; • a first set of friction discs (1403) comprises a second external toothing (1405), and a second set of friction discs (1402) comprises a second internal toothing (1406); and • the first external toothing cooperating with the second internal toothing (1406) and the first internal toothing cooperating with the second external toothing (1405).

10. Differential module (2) according to any one of claims 8 and 9 in combination with claim 3, the actuation system (22) comprising a movable support means (2201) configured to exert a support on the friction discs (1401) of the clutch (14), said movable support means (2201) passing through openings (1504) provided in the rotating support (15).

11. Torque transmission system, particularly for automobiles, comprising a differential module (2) according to any one of the preceding claims and further comprising: • a gear set (7) capable of cooperating kinematically in rotation with a traction motor (5) on the one hand and with the differential module (2) on the other hand to form one or more speed reduction ratios; • a transmission housing (6) in which the gear set (7) and the differential module (2) are housed.

12. Powertrain (1) comprising a traction motor (5) and a torque transmission system according to the preceding claim.

Images