Limited slip differential module

Abstract

The invention relates to a differential module comprising: a housing (9) receiving a torque supplied by a traction motor; at least one planetary pinion (11) pivotally mounted on the housing (9); first and second planetary pinions (12, 13) meshing with the at least one planetary pinion and rotating a first and a second wheel drive half-shaft (3, 4); and a clutch (14) configured to transmit and / or interrupt a 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 providing limited slip and locking capabilities. Technological background

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

[0003] To address this situation, limited slip differentials have been developed to transfer power from the drive wheel that has lost grip and tends to spin out of control to the drive wheel that is not spinning.

[0004] It is known, in particular from document US6561939, such a limited slip differential device intended to transmit and distribute a torque coming from an engine to two wheel drive half-shafts of an axle of the vehicle. The device comprises a housing driven in rotation by a traction motor and containing two planetary pinions meshing with two planetary pinions. Each planetary pinion is configured to drive a wheel drive half-shaft of the axle of the vehicle. A multi-disc clutch controlled by an actuation system is arranged to selectively couple, for example when a wheel loses grip, the housing with a wheel drive half-shaft.Half of the friction discs of the multi-disc clutch are provided with external teeth which cooperate in rotation with an external disc carrier fixed integrally to the housing, and the other half of the friction discs of the multi-disc clutch are provided with internal teeth which cooperate in rotation with a splined sleeve linked in rotation to a wheel drive half-shaft.

[0005] Such a limited slip differential device structure poses several technical problems, firstly its insufficient compactness. Indeed, the arrangement of such a structure leads to having to axially superimpose the differential housing, the clutch and the actuation system. This therefore implies a significant overall dimensions in the axial direction which may prove incompatible with the very limited space allocated to recent transmissions, particularly transmissions for electric vehicles. In parallel with the improvement in compactness, the limited slip differential device must be simpler and more economical to produce. Summary

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

[0007] An idea underlying the invention is a limited slip differential module which 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 transmission system of a vehicle, the differential module having a first axis of rotation and comprising: • a box receiving a torque supplied, directly or indirectly, by a traction motor; • at least one satellite pinion mounted on the housing and pivoting around a second axis of rotation; • a first and a second planetary pinion pivoting about the first axis of rotation and meshing with the at least one satellite pinion, the first and the second planetary pinion driving in rotation respectively a first and a second wheel drive half-shaft; and • a clutch configured to transmit and / or 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 torque input element being supported by a radially outer surface of the housing.

[0009] Thanks to the architecture according to the invention, the housing supports both the at least one satellite pinion and the torque input element. This therefore makes it possible to achieve 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 intersecting 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 qualified as internal as opposed to an external component located radially on the periphery; • “rotationally linked” means “assembled so that they do not rotate one by one” relation to the other”. In other words, it is a rotationally solid connection, possibly presenting a very small clearance such as a groove clearance; • two parts are said to be “fixed” when they are permanently immobilized relative to each other, this immobilization being able to result from a fixing of the first part on the second part directly or by means of 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 made in one piece with the housing, the torque input element being obtained in particular by a method 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, by shrinking, by screwing, by riveting or by crimping.

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

[0014] According to an additional characteristic 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 characteristics, the clutch can have an axially recentered position relative to the differential pinions, which makes it possible to reduce the axial dimension of the housing necessary to ensure the support of both the at least one satellite pinion and the torque input element.

[0016] Furthermore, positioned in this way, the clutch is located on a large diameter, which gives it increased torque capacity.

[0017] According to an additional characteristic of the invention, the torque output element is carried by a support rotating about the first axis of rotation, the rotating support comprising at least one radially internal surface radially surrounding the housing, the radially internal surface being spaced from the housing by a radial clearance.

[0018] Thus defined, the shape of the rotary support combined with the shape of the housing advantageously makes it possible to provide a radial space used to house the clutch. The radial clearance makes it possible to avoid any contact between the housing and the rotary support, these two parts being able to rotate at different speeds.

[0019] According to one aspect of the invention, the torque output element carried by the rotary support is made in one piece with the rotary support, the torque output element being obtained in particular by a method of removing or deforming material from the rotary support.

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

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

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

[0023] By virtue of this feature, the transmission of torque from the torque output element to the second wheel drive half-shaft can be ensured directly. By using a spline, assembly is made easy by allowing the rotary support to be plugged into the second wheel drive half-shaft.

[0024] According to an additional characteristic of the invention, the rotary support and the housing are radially centered relative to each other by at least one first bearing.

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

[0026] According to an additional characteristic of the invention, the rotary support is able to be supported by a transmission casing via at least a second bearing, and the housing is able to be supported by the transmission casing via at least a third bearing.

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

[0028] According to an additional characteristic of the invention, the clutch is actuated by an actuating system, the actuating system being supported by the rotary support via a fourth bearing.

[0029] This characteristic allows in particular that the actuation system can be integrated into the subassembly constituted by the differential module.

[0030] According to an additional characteristic 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 fully closed, as well as easy modulation of the level of torque transmitted depending on the conditions of use of the vehicle thanks to the possibility of sliding the discs between them.

[0032] According to an additional characteristic of the invention: • the torque input element forms a first external toothing, and the torque output element 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 toothing cooperating with the second internal toothing and the first internal toothing cooperating with the second external toothing.

[0033] According to an additional characteristic of the invention, the actuation system comprises a mobile support means configured to exert pressure on the friction discs, said mobile support means passing through openings provided in the rotary support.

[0034] This feature allows the integration of the actuation system on the rotary support in a compact manner.

[0035] The differential module according to the invention may have one or other of the characteristics described below combined with each other or taken independently of each other: the at least one satellite pinion and the two planetary pinions may be bevel gears; the at least one satellite pinion is pivotally mounted on a cylindrical rod fixed to the housing; the number of satellite gears is between one and twelve, notably four; the at least one satellite pinion and the two planetary pinions can be produced in the form of cylindrical gears, in particular straight-toothed gears, in particular gears arranged in the form of an epicyclic gear train; the housing comprises an internal cavity in which at least one satellite pinion and the two planetary pinions are housed; the two planetary gears are supported by the housing; the housing can be made of several parts, fixed together by a fixing means, in particular by welding or by screwing or by riveting; a gear wheel is attached to the housing, the gear wheel receiving, via a set of gears, the torque supplied by the traction motor;

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[0046] • the first, second, third and fourth bearings may be plain bearings or ball bearings or roller bearings or a sliding liner; • 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 clutch or dog clutch; • the actuation system can be mechanical, electromechanical, electromagnetic, pneumatic or even hydraulic; • the actuation system may include a ball ramp; The invention further relates to a torque transmission system, in particular for an automobile, comprising a differential module as defined previously 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 housing in which the gear set and the differential module are housed. The invention further relates to a powertrain comprising a traction motor and a torque transmission system as defined above. Brief description of the figures [Fig.l] [Fig.l] illustrates a schematic sectional view of a powertrain comprising a differential module according to the invention. [Fig.2a] [Fig.2a] is a sectional view of the differential module according to the invention. [Fig.2b] [Fig.2b] is a detail view of [Fig.2a]. [Fig.2c] [Fig.2c] is another detail view of [Fig.2a]. [Fig.3] [Fig.3] is a cutaway perspective view of the differential module according to the invention. [Fig.4] [Fig.4] is a perspective view of the housing of the differential module according to the invention. [Fig.5] [Fig.5] is a cutaway perspective view of the rotating support of the differential module according to the invention. [Fig.6] [Fig.6] is a perspective view of the friction discs of the clutch of the differential module according to the invention. Description of the embodiments In all figures, elements that are identical or provide the same function are marked the same reference numbers. The following embodiments are examples. Although the description refers to one or more embodiments, this does not necessarily mean that each reference relates to the same embodiment or that the features apply only to a single embodiment. Single features of different embodiments may also be combined or interchanged to provide other embodiments.

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

[0048] Such a differential module 2 is for example intended for a hybrid vehicle. Thus, the powertrain 1 is, for example, capable of transmitting torque from an electric motor to a rear or front axle of the vehicle while another powertrain coupled to another engine, such as a heat engine, makes it possible to generate torque and transmit it between this other engine and the wheel drive half-shafts 3, 4 of the other axle of the vehicle. Another powertrain configuration for a hybrid vehicle may consist of the association of a heat engine and an electric motor, both associated to transmit torque to the wheel drive half-shafts 3, 4 of the same axle. The vehicle may also be fully electric.

[0049] As visible in [Fig.l], the powertrain 1 comprises a transmission casing 6 in which a traction motor 5, a differential module 2 and a set of gears 7 are housed. The structure of the transmission casing 6 may be in one piece or composed of several sub-parts. The traction motor 5 comprises at its output a shaft rotating around a third axis of rotation X3. The set of gears 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.l], the gear set 7 comprises a first cylindrical gear train 701, coaxial with the third axis of rotation X3, and cooperating kinematically in rotation with a second cylindrical gear train 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 cylindrical gear train 702 cooperates kinematically in rotation with a toothed wheel 8 secured to a housing 9 of the differential module 2 to form a second reduction ratio.

[0051] In this example, the traction motor 5 may be an electric or thermal motor. Another electric or thermal motor (not shown) may additionally be coupled with one of the gears of 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 toothed wheel 8 a torque supplied by the traction motor 5, two planetary pinions 11 mounted on the housing 9 and pivoting about a second axis of rotation X2, a first and a second planetary pinions 12, 13 pivoting about the first axis of rotation XI and meshing with the two planetary pinions 11, the first and the second planetary pinions 12, 13 driving in rotation respectively a first and a second wheel drive half-shaft 3, 4 and a clutch 14 configured to transmit and / or interrupt a passage of at least a part of the torque from the housing 9 to the second wheel drive half-shaft 4 or from the housing 9 to the second planetary pinion 13, the clutch 14 comprising 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.,

[0053] In this embodiment, the housing 9 can form a cavity which houses and supports the satellite pinions 11 and the planetary pinions 12, 13. The satellite pinions 11 and the planetary pinions 12, 13 are here bevel gears. A cylindrical rod 902 can be fixed to the housing 9, the satellite pinions 11 being pivotally mounted about the second axis of rotation X2 on said cylindrical rod 902. The satellite pinions 11 can be one to four in number, the choice of a number of four having the advantage of being able to transmit the torque with satellite pinions of smaller dimensions. 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 rotatably connected to the two wheel drive half-shafts 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 in order to limit the wear and friction generated by the relative movement of the parts. The gear wheel 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 pinions and the planetary pinions are produced 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 planet 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 torque output element 1501 may be carried by a rotary support 15 around the first axis of rotation XL. The rotary support 15 may comprise a radially internal surface 1502 radially surrounding the housing 9. A radial clearance J is provided between the housing 9 and the rotary support 15 in order to avoid any direct contact between these two parts which may rotate at different speeds.

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

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

[0059] The clutch 14 is actuated by an actuation system 22. The actuation system 22 may be supported by the rotary support 15 via a fourth bearing 23, here a ball bearing. The actuation system 22 may 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 support on the friction discs 1401 of the clutch 14, said movable support means 2201 passing through openings 1504, (visible in [Fig. 5]), arranged in the rotary support 15.

[0060] The actuation system 22 may be of the mechanical, electromechanical, electromagnetic, pneumatic or even hydraulic type. As illustrated in [Fig.2c], the actuation system 22 may be formed by a ball ramp which comprises a first ramp 2202 and a second ramp 2203. A ring 2204 between the first ramp 2202 and the second ramp 2203 holds balls 2205. The first ramp 2202 is configured to be driven in rotation about the first axis of rotation XI, directly or indirectly, by an actuator motor (not shown). The second ramp 2203 is stopped in rotation by the transmission casing 6 and is configured to translate axially. The second ramp 2203 is linked to the movable support means 2201 via a second axial bearing 2206, here an axial needle thrust bearing. The ramps 2202 and 2203 have adapted shapes so that, when set into relative rotation by the actuator motor, these ramps allow the mobile support means 2201 to be moved axially.

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

[0062] Similarly, as illustrated in [Fig.5], the torque output element 1501 may be made in one piece with the rotary support 15. Here, the torque output element 1501 is produced in the form of a second internal toothing, for example obtained by stamping the rotary 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 rotary support 15. The plurality of friction discs 1401 is composed of a first set of friction discs 1403 comprising a second external toothing 1405 cooperating with the torque output element 1501 formed by the first internal toothing of the rotary support 15, and a second set of friction discs 1402 comprising 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 emerge for a person skilled in the art from the present description, the drawings and the attached claims, even if concretely they have only been described in relation to other determined 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 cannot be interpreted as a limitation of the claim.

Claims

Claims

1. Differential module (2) for a transmission system of a vehicle, the differential module (2) having a first axis of rotation (XI) and comprising: • a housing (9) receiving a 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); • first and second planetary pinions (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) rotating respectively a first and a second wheel drive half-shaft (3, 4);and • a clutch (14) configured to transmit and / or 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); characterized in that the torque input element (901) is supported by a radially external surface (905) of the housing (9).;

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

3. Differential module (2) according to claim 1 or 2, wherein the clutch (14) is positioned axially so that it is crossed by a plane perpendicular to the first axis of rotation (X1) and passing through the second axis of rotation (X2).

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

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

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

7. A differential module (2) according to any one of claims 4 to 6, wherein the rotatable support (15) is adapted to be supported by a transmission housing (6) via at least one second bearing (19), and the housing (9) is adapted to be supported by the transmission housing (6) via at least one third bearing (20).

8. A differential module (2) according to any one of claims 4 to 7, wherein the clutch (14) is actuated by an actuation system (22), the actuation system (22) being supported by the rotary support (15) via a fourth bearing (23).

9. A differential module (2) according to any preceding claim, wherein the clutch (14) comprises a plurality of stacked friction discs (1401).

10. A differential module (2) according to claim 9, wherein: • the torque input element (901) forms a first external toothing, and the torque output element (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).

11. Differential module (2) according to one of claims 9 and 10 in combination with claim 4, the actuation system (22) comprising a movable support means (2201) configured to exert a pressure on the friction discs (1401) of the clutch (14), said movable support means (2201) passing through openings (1504) arranged in the rotating support (15).

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

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

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