Patent Description:
A vehicle such as a truck is generally equipped with one or several differential units on its driven axles, to allow the left and right wheels of said axle to have different speeds when turning/manoeuvring.

Differential assemblies are disclosed in <CIT>,_<CIT> and <CIT>.

As the transverse width of a vehicle, in particular a truck, is limited to a maximum value given by regulatory requirements, other vehicle components need to be fairly compact, which in particular applies to the powertrain system, especially the differential unit.

Such a space constraint is even more significant in some vehicle configurations:.

A trend in transport industry, in particular in heavy duty transport industry, is to move from rigid axles to independent wheel suspension configurations, to improve several features (dynamic behavior, volume capacity for battery / fuel, wheel alignment, comfort, etc.). To get maximized battery / fuel efficiency from an independent wheel suspension driveline, wheel reduction (hub reduction) should be avoided. Without such a wheel reduction, the drive shafts have to be bigger. Moreover, these drive shafts must have a minimum length to support driveline torque and keep acceptable working angles, in order not to compromise the suspension stroke and consequently the comfort.

The width of vehicle being legally constrained, and a minimum length being needed for the drive shaft for torque and angle constraints, there is a need for an as much as possible compact differential unit in the vehicle transverse direction.

Other constraints derive from the independent wheel suspension configuration, such as the need for a stronger support of the drive shafts both in the differential unit area and in the wheel area, or the need to secure each drive shaft in translation, in both directions along the vehicle transverse direction and without play, in the differential unit, to avoid a greatly limit wear.

All these requirements have to be taken into account, bearing in mind that the mounting process of the whole vehicle driven wheel system must preferably not be significantly complicated nor take much longer. The same applies to maintenance operations.

An object of the invention is to provide an improved axle system for a vehicle which solves at least one of the problems of the prior art.

In particular, the invention aims at improving compactness, and at making the mounting process and/or the maintenance operations easier.

To that end, and according to a first aspect, the invention concerns an axle system for a vehicle, as set forth in claim <NUM>.

Providing an axle system including a first bearing, in addition to the second bearing, makes it possible to better support and guide the drive shaft in rotation inside the differential. Owing to the invention, this advantage is not obtained to the detriment of compactness, as explained below.

Indeed, by providing a first bearing having a smaller outer diameter than the radial dimension of the joint, the invention greatly improves the compactness. As a result, the differential unit is more compact in the radial direction but also as a whole. Indeed, a small first bearing can more easily be housed in a limited space and, in some embodiments, can be appropriately and efficiently arranged relative to the surrounding components to further limit compactness, including in other directions than the radial direction. Besides, as the first bearing has a fairly small outer diameter, it does not require other components of the differential unit to be sized as large and/or resistant parts. Therefore, the overall size, weight and cost of the differential unit are reduced.

However, with such a configuration, due to its small outer diameter, the fist bearing can be hidden by the joint or another component of the axle system, when looking axially towards the differential unit. As a consequence, the first bearing cannot be accessed nor easily axially blocked by conventional tightening means.

This is the reason why the invention further provides a specific tightening member having a specifically designed manoeuvring portion for allowing a user to easily and efficiently tighten said tightening member. In concrete terms, the terms "arranged in an offset relation relative to the joint" mean that the manoeuvring portion and the joint are not superimposed, or at least partially not superimposed, when looking axially towards the differential unit.

The tightening member is used to axially lock the first bearing outer ring relative to the first housing, i.e. to axially maintain the first bearing outer ring relative to the first housing, in both directions, without play. This prevents or greatly limits wear on the components due to high axial forces, in both directions and at high frequency.

The invention thus makes it possible to improve compactness without negative effects on the assembly and structure quality of the axle system nor on the ease of the mounting process.

"Axle system" has to be understood as the set of pieces that joins two wheels, and is not limited to a rigid axle. In the present invention, the axle system is not rigid as the drive shafts include joints. In practice, the axle system comprises two drive shafts, one on each side of the differential unit. The joint can be a universal joint, a homocinetic joint, a Rzeppa joint, or any other kind of joint capable of coupling connecting rigid rods whose axes are inclined to each other and to transmit rotary motion between said rigid rods.

"Differential unit" refers to a unit providing a differential effect, in order to allow the outer drive wheel to rotate faster than the inner drive wheel during a turn. Such a differential unit can include a mechanical differential. Alternatively, the differential effect can be achieved by the fact that the wheels are driven independently by a dedicated motor, preferably but not exclusively an electric motor, and corresponding transmission system, in a so-called torque vectoring technology.

In concrete terms, the radial dimension of the joint is the diameter of the smallest cylinder which has its centre on the axis, and which fully contains the joint, when the drive shaft is in a straight configuration (also called "enveloping cylinder"). The joint is not necessarily a rotationally symmetric piece; it can have at least a first radial dimension along one direction, and a second radial dimension different from the first radial dimension along another direction. The largest dimension among the first and the second radial dimensions is then the joint radial dimension.

In practice, the second housing can be an outer part that does not rotate relative to the vehicle chassis, while the first housing can be an inner rotating part relative to the vehicle chassis.

According to an embodiment, the first bearing outer diameter can be smaller than the second bearing inner diameter. Such a configuration allows reducing the space required in the radial direction.

In addition, advantageously, the first bearing and the second bearing may have median planes which are orthogonal to the axis and which are substantially coincident. In other words, with this configuration, the first bearing is arranged inside the second bearing. This further reduces the space required in the transverse direction. The term "coincident" includes a configuration in which the median planes are offset by less than <NUM> % of the axial length of the first bearing, preferably less than <NUM> %, more preferably less than <NUM> %.

The first housing may comprise a radial wall, the tightening member being configured to axially tighten the first bearing outer ring against said radial wall. Said radial wall may be a piece distinct from the first housing but secured to the first housing. Said radial wall - which extends in a plane orthogonal to the axis - thus forms an axial abutment.

The tightening member manoeuvring portion can comprise at least one hole, recess or the like, configured to receive a tool capable of moving the tightening member axially relative to the first housing.

The tightening member can comprise several manoeuvring portions which are all arranged in an offset relation relative to the joint, and which are preferably arranged substantially on one and the same circle.

The axle system can comprise several tightening members, each tightening member comprising at least one manoeuvring portion which is arranged in an offset relation relative to the joint, the tightening members preferably being arranged substantially on one and the same circle.

The term "circle" is not limited to a line but includes an annular zone having a small radial dimension.

The axle system may further comprise a seal arranged between the drive shaft - or a part secured to the drive shaft - and the second housing - or a part secured to the second housing, the seal preferably having an annular shape.

The axle system may further comprise a cover having an opening for receiving the drive shaft, the cover being configured to be removably mounted on and/or fastened to the second housing after the tightening phase of the axle system mounting process. In an embodiment, the cover may cover the manoeuvring portion. However, other implementations may be envisaged. The cover can have an annular shape, the opening being then centrally arranged in the cover.

The seal may be mounted in the cover opening. In an embodiment, the annular seal is mounted in the central opening of the annular cover.

In an implementation, the axle system comprises a left drive shaft connected to the differential unit and configured to be connected to at least one left wheel, and a right drive shaft connected to the differential unit and configured to be connected to at least one right wheel, the differential unit further comprising a differential which mechanically links the two drive shafts. At least one of the drive shafts is made to rotate:.

The differential may further comprise a blocking system for blocking the differential operation.

In another implementation, the differential effect is not achieved by means of a differential but through torque vectoring technology. Then, the axle system comprises a left drive shaft connected to the differential unit and configured to be connected to at least one left wheel, and a right drive shaft connected to the differential unit and configured to be connected to at least one right wheel. The differential unit further comprises at least one motor (electric motor, hydraulic motor, etc.) capable of rotating the left drive shaft through a transmission system, and at least one motor (electric motor, hydraulic motor, etc.) capable of rotating the right drive shaft through a transmission system, independently from the left drive shaft.

According to a first embodiment of the invention, the manoeuvring portion of the tightening member is located in an area of the tightening member which is radially outside from the joint enveloping cylinder - i.e. the smallest cylinder which has its centre on the axis, and which fully contains the joint - when looking axially towards the differential unit. In other words, said area of the tightening member is radially outwardly offset from the joint. For example, said manoeuvring portion can be located in an annular area having a diameter that is larger than the radial dimension of the joint.

The manoeuvring portion of the tightening member can be located in a peripheral area of the tightening member.

For example, the tightening member can comprise a nut having:.

The annular seal may have an inner diameter that is larger than the radial dimension of the joint. This disposition is advantageous in that the annular seal may be replaced when needed without disassembling the drive shaft. The maintenance is thus significantly improved.

The axle system may comprise a contact piece secured around the drive shaft and having:.

By providing a contact portion which is radially inwardly offset relative to the tightening member manoeuvring portion, the invention ensures that access to the manoeuvring portion is not impeded by the contact piece. In other words, the contact piece can be mounted before the tightening phase. For example, there may be provided several manoeuvring portions arranged substantially on one and the same circle (or annular area) having a larger diameter than the contact portion.

In use, the contact portion of the contact piece can turn inside and against the annular seal; the annular seal and the annular cover can hide the tightening member manoeuvring portion.

According to a second embodiment of the invention, when looking axially towards the differential unit, the manoeuvring portion of the tightening member is located in an area at least partially included in the joint enveloping cylinder - i.e. the smallest cylinder which has its centre on the axis, and which fully contains the joint -and the manoeuvring portion of the tightening member is circumferentially offset from the joint or each portion of the joint. As the manoeuvring portion is located in an area at least partially included in the joint enveloping cylinder, it would not be accessible for being tightened if not circumferentially offset from the joint or each portion of the joint.

The tightening member can comprise at least one plate configured for abutting against the outer ring of the first bearing, the plate being preferably substantially flat, and preferably having a transverse dimension less than the inner diameter of the first bearing. The "transverse dimension" means the dimension in a transverse plane, i.e. a plane orthogonal to the axis. In concrete terms, the plate can be disc-shaped, its transverse dimension then being its diameter.

In other words, the plate is preferably a localized and separate piece. For example, the plate can be disc shaped. It can comprise at least one hole - for example two holes - for receiving a screw or another fastener. There may preferably be provided several distinct plates (for example four plates) regularly arranged around the axis.

The annular cover can comprise at least one aperture substantially axially facing the tightening member, so as to allow access to the manoeuvring portion. For example, the plate can have the same shape and dimensions that the aperture, so that it can be engaged through the aperture.

The annular seal may have an inner diameter that is smaller than the radial dimension of the joint. With such a configuration, the annular seal cannot be removed after the mounting process has been completed. However, a smaller seal is more energy efficient and accepts higher rotational speeds.

The drive shaft can comprise a stepped portion including a transverse face which forms an axial abutment for the first bearing, and a cylindrical face which forms a contact portion with which the annular seal is in contact, the diameter of the cylindrical face being equal or larger than the first bearing inner diameter. Preferably, the outer diameter of the annular seal is smaller than the first bearing outer diameter. The first bearing is thus hidden by the joint, the annular seal and the annular cover.

In use, the contact portion of the drive shaft stepped portion turns inside and against the annular seal.

According to a second aspect, it is described a drive shaft sub assembly for an axle system as previously described, the drive shaft sub assembly comprising a drive shaft, wherein the drive shaft has one end configured to be connected to a vehicle wheel and one end connected to a differential unit of the axle system, the drive shaft including at least one joint connecting two portions of the drive shaft to transmit rotary motion between said portions, the joint having a radial dimension.

The drive shaft sub assembly may comprise:.

Both the tightening member and the contact piece can be located between the first bearing and the joint; a nut can be provided on the side of the ring that is opposite the contact piece, in the axial direction.

Alternatively, the drive shaft sub assembly may comprise:.

According to a third aspect, the invention concerns a driven wheel system for a vehicle, comprising an axle system as previously described, at least one left wheel and at least one right wheel, the axle system comprising a left drive shaft connected to the differential unit and to the left wheel(s), and a right drive shaft connected to the differential unit and to the right wheel(s), each wheel being further connected to the differential unit by at least one lower arm articulated at both ends and preferably at least one upper arm articulated at both ends.

According to a fourth aspect, the invention concerns a vehicle comprising at least one driven wheel system as previously described.

According to a fifth aspect, the invention relates to a process for mounting an axle system as previously described, the process comprising the following steps:.

Owing to the invention, the drive shaft can be mounted at a late step of the mounting process, which makes said process significantly easier. Indeed, the number of subsequent mounting steps to be performed with the drive shaft already assembled, i.e. to be performed with a heavy and cumbersome system, are limited. The invention thus meets the strong demand to have the drive shaft kept as pre-assembled units (as these drive shafts need to be dynamically equilibrated) without significant negative impact on the mounting process.

According to an embodiment, in step c), the tightening member is provided as a piece mounted on the drive shaft, before the drive shaft sub-assembly is engaged in the first housing.

According to another embodiment, in step c), the tightening member is provided as a separate piece, and in that the tightening member is assembled to the axle system once the drive shaft sub-assembly has been engaged in the first housing. By "separate piece" is meant that the tightening member is not fastened to another piece (of the differential unit or of the drive shaft sub-assembly).

The invention can be applied in heavy-duty vehicles, such as trucks, buses and construction equipment, as well as medium-duty vehicles.

As shown in <FIG>, a vehicle <NUM> comprises at least one driven wheel system <NUM>. In the illustrated embodiment, the vehicle <NUM> comprises a first driven rear wheel system 6a and a second driven rear wheel system 6b located rearwards from the first driven rear wheel system 6a. The vehicle <NUM> further includes a front axle <NUM> connected to front wheels <NUM>.

Although the invention is described for a rear driven wheel system, it can be used in another driven wheel system, especially in a front driven wheel system.

The or each driven wheel system <NUM> has an axis <NUM>, and comprises a differential unit <NUM>, i.e. a unit providing a differential effect, in order to allow the outer drive wheel to rotate faster than the inner drive wheel during a turn.

The driven wheel system <NUM> further comprises two drive shafts <NUM>, namely a left drive shaft connected to the differential unit <NUM> and to at least one left wheel <NUM>, and a right drive shaft connected to the differential unit <NUM> and to at least one right wheel <NUM>. Each rear wheel system 6a, 6b can comprise two wheels <NUM> on either side, thus forming a dual mounted tires arrangement. However, this should not be considered as limitative.

In the embodiment illustrated in <FIG>, the vehicle <NUM> comprises an engine <NUM> that drives an input shaft <NUM> having an axis <NUM>. The differential unit <NUM> includes a differential <NUM> which is driven by the input shaft <NUM> and which transmits the appropriate torque to the left and right drive shafts <NUM>. An additional shaft <NUM> connects the input shaft <NUM> to the differential unit <NUM> of the second driven rear wheel system 6b, through the differential unit <NUM> of the first driven rear wheel system 6a, and is the input shaft for the differential unit <NUM> of the second driven rear wheel system 6b.

Alternatively, as will be described with reference to <FIG>, the invention can be applied to an electric vehicle. Such a vehicle does not include an engine <NUM> nor the corresponding driveline, but rather at least one electric motor. Either one motor (or more) is used to drive a corresponding drive shaft <NUM>, the drive shafts thus being independently driven by one or more dedicated motors, with the appropriate torque (see <FIG>); or one motor (or more) is used to drive a mechanical differential rotating the drive shafts <NUM> with the appropriate torques (variant not illustrated).

The invention concerns a vehicle <NUM> having an independent wheel configuration, as schematically illustrated in <FIG>. In such a configuration, the left wheel(s) <NUM> and the right wheel(s) <NUM> are each connected to the differential unit <NUM> by means of the corresponding driveshaft <NUM>, at least one joint <NUM> (such as a universal i.e. a cardan joint, or another kind of joint), at least one lower arm 14b articulated at both ends, and preferably at least one upper arm 14a articulated at both ends. Although in <FIG> the differential unit <NUM> is shown as including a differential <NUM>, other implementations are possible.

As shown in <FIG>, the drive shaft <NUM> comprises a first end <NUM> configured to be connected to the differential unit <NUM> and a second end <NUM> configured to be connected to a wheel <NUM> of the vehicle <NUM>. The first end <NUM> and the second end <NUM> may be provided with splines <NUM> or another system providing a rotationally blocked connection with the differential unit <NUM> / the wheel <NUM>.

The drive shaft <NUM> is made of several rigid portions <NUM>. In the embodiment illustrated in <FIG>, there are provided a first portion 114a configured to be connected to the differential unit <NUM>, a second portion 114b configured to be connected to a wheel <NUM>, and two intermediate portions 114c, 114d, which are movable the one into the other along axis <NUM> to form a telescopic intermediate piece, in order to adjust the drive shaft length to the suspension stroke. The first portion 114a has an axis <NUM>.

As can be seen in <FIG>, the longitudinal direction X is defined as a direction parallel to the axis <NUM> of a driven wheel system <NUM>, which joins the wheels <NUM> when the drive shaft <NUM> is in a straight configuration as illustrated in <FIG>. In the operating position, i.e. when the differential unit is mounted under the vehicle <NUM>, as shown in <FIG>, the longitudinal direction X corresponds the transverse direction Y' of the vehicle <NUM>. Direction X is substantially horizontal when the vehicle <NUM> is on a horizontal surface.

Besides, the transverse direction Y is defined as the direction which is orthogonal to the longitudinal direction X and substantially horizontal when the vehicle <NUM> is on a horizontal surface. Direction Y corresponds the longitudinal direction X' of the vehicle <NUM>. The axis <NUM> of the input shaft <NUM> is roughly parallel to the transverse direction Y, i. e the longitudinal direction X' of the vehicle <NUM>, or inclined relative to the transverse direction Y, horizontally and/or vertically, by preferably less than <NUM>°.

Moreover, direction Z is defined as the vertical direction - when the vehicle <NUM> is on a horizontal surface.

The invention will be described when the vehicle <NUM> is on a horizontal surface.

Portion 114a and portion 114d, on the one hand, and portion 114b and portion 114c, on the other hand, are connected by a joint <NUM>. In the embodiment illustrated in the figures, each joint <NUM> is a universal joint. However, this should not be considered as limitative; any other type of joint which is configured for transmitting rotary motion between said adjacent portions <NUM> could be implemented.

The joint <NUM> has a radial dimension D, which is defined as the largest dimension of the joint <NUM> in a plane (Y,Z). In other word, the radial dimension is the diameter of the smallest cylinder C (called "enveloping cylinder") which has its centre on the axis <NUM>, and which fully contains the joint <NUM>, when the drive shaft has a straight configuration.

For example, with a universal joint as illustrated in <FIG>, the joint <NUM> comprises two U-shaped pieces <NUM>, <NUM> each having a median plane, the median planes being orthogonal the one relative to the other. One U-shaped piece <NUM> has a radial length D1, i.e. the radial length between the ends of the U; the other U-shaped piece <NUM> has a radial length D2 which is larger than D1. In this embodiment, the radial dimension D of the joint <NUM> is defined along a direction which is inclined relative to the directions along which D1 and D2 are defined; D is a bit higher than D2.

Reference is now made to <FIG> which show a first embodiment of the invention. <FIG> more specifically illustrates an axle system <NUM> including a differential unit <NUM> and one drive shaft <NUM> on both sides of the differential unit <NUM>.

One variant of this first embodiment is illustrated in <FIG>.

The differential unit <NUM> comprises a differential carrier housing <NUM>, which can made of a first housing portion 20a and a second housing portion 20b (also shown in <FIG>) secured to one another by means of appropriate fasteners (not shown). In another implementation, the differential carrier housing <NUM> can made of a single piece.

The differential unit can comprise a differential <NUM> - i.e. a mechanical differential.

Inside the differential carrier housing <NUM> can be located a crown wheel <NUM> having a longitudinal axis <NUM>. The crown wheel <NUM> is driven in rotation around said longitudinal axis <NUM> by the input shaft <NUM>, by engagement of teeth arranged on a pinion <NUM> mounted on said input shaft <NUM> and teeth arranged on the crown wheel <NUM>.

Inside the crown wheel <NUM> is arranged the differential <NUM> which comprises differential side pinions <NUM>, for example four differential side pinions, which are fitted on a joint cross <NUM> attached to the crown wheel <NUM>, and two differential side gears <NUM>. Each differential side gear <NUM> meshes with at least one differential side pinion <NUM> and is fastened to the first end <NUM> of one of the drive shafts <NUM>, i.e. to the first end <NUM> of the portion 114a of the drive shaft <NUM>. In the mounted position, the axis <NUM> of said portion 114a and the axis <NUM> of the crown wheel <NUM> are coincident.

The differential unit <NUM> further comprises, inside the differential carrier housing <NUM>, a differential housing arrangement <NUM> which contains the differential <NUM> and part of the drive shafts <NUM>, more specifically part of the portion 114a of each drive shaft <NUM>. The differential housing arrangement <NUM> is secured to the crown wheel <NUM>. It may be made of two parts, namely two differential housings 24a, 24b each forming a sleeve around the corresponding differential side gears <NUM> and partly around the drive shaft <NUM>. Said differential housings 24a, 24b may be fastened on both sides of the joint cross <NUM>; other implementations may however be envisaged.

Thus, on each side of the joint cross <NUM>, the differential side gear <NUM> is mounted at the first end <NUM> of the drive shaft <NUM> in a rotationally fixed manner, for example by means of the splines <NUM>. Furthermore, both the differential side gear <NUM> and the drive shaft <NUM> are rotatably mounted relative to the differential housing 24a, 24b around the longitudinal axis <NUM>. The crown wheel <NUM>, differential <NUM>, and differential housing <NUM> are rotating parts inside and with respect to the differential carrier housing <NUM>.

In this application, the differential housing <NUM> is also referred to as "first housing <NUM>", while the differential carrier housing <NUM> is also referred to as "second housing <NUM>".

The differential unit <NUM> may further comprise a blocking system <NUM> for blocking the differential unit operation, when required.

It has to be noted that, according to an alternative implementation of <FIG>, not show, the first housing <NUM> and joint cross <NUM> could be made to rotate not by a crown wheel driven by the engine <NUM>, but by an motor (electric motor, hydraulic motor, etc.). In such a configuration of the vehicle <NUM>, the motor output shaft may be mechanically connected to the first housing <NUM> and joint cross <NUM> by means of a transmission system preferably including a gear system.

The way one drive shaft <NUM>, more precisely the portion 114a of the drive shaft <NUM>, is arranged in the differential unit <NUM> will now be described, bearing in mind that the left and right arrangements are structurally identical, while their respective dimensions may be different.

The axle system <NUM> comprises a first bearing <NUM> which is secured around the drive shaft <NUM>, and placed between the drive shaft <NUM> and the first housing <NUM>. The drive shaft <NUM> is thus rotationally received in the first housing <NUM>. The first bearing <NUM> includes an inner ring <NUM> and an outer ring <NUM>, as well as rolling elements <NUM> which may be balls.

The first bearing inner ring <NUM> is rotationally fastened to the drive shaft <NUM> and further axially fastened to the drive shaft <NUM>. To that end, the first bearing inner ring <NUM> may be pushed against a shoulder <NUM> of the drive shaft <NUM> - forming a radial abutment - by means of an appropriate element such as nut <NUM>. The first bearing inner ring <NUM> may be in contact with the shoulder <NUM> (see for example <FIG>), or an intermediate piece may be provided between the inner ring <NUM> and the shoulder <NUM> (see for example <FIG>).

The axle system <NUM> also comprises a second bearing <NUM> which is placed between the first housing <NUM> and the second housing <NUM>. The second bearing <NUM> includes an inner ring <NUM> and an outer ring <NUM>, as well as rolling elements <NUM> which may be tapered rollers.

In a particularly compact non limitative embodiment, the outer diameter D30 of the first bearing <NUM> is smaller than the inner diameter D41 of the second bearing <NUM>. Furthermore, the first bearing <NUM> and the second bearing <NUM> may have median planes P30, P40, respectively, which are orthogonal to the axis <NUM> and which are substantially coincident. Thus, the first bearing <NUM> and the second bearing <NUM> can be arranged coaxially the one inside the other. This significantly improves compactness, specifically in the longitudinal direction X (i.e. the transverse direction Y' of the vehicle <NUM>).

According to the invention, the outer diameter D30 of the first bearing <NUM> is smaller than the radial dimension D of the joint <NUM>. Having a small bearing is advantageous, especially in terms of compactness, but the consequence is that access to the first bearing <NUM> is complicated, or even impossible, when the drive shaft <NUM> is mounted in the first housing <NUM>. As the first bearing <NUM> is generally secured around the drive shaft <NUM> before the drive shaft <NUM> is inserted inside the first housing <NUM>, then the first bearing <NUM> is necessarily hidden, or hard to access, when it is located in the first housing <NUM>. However, the first bearing <NUM> has to be maintained axially, without mechanical play, for an efficient and robust implementation of the axle system <NUM>.

To solve this problem, there axle system <NUM> comprises at least one tightening member <NUM> configured to axially lock the first bearing outer ring <NUM> relative to the first housing <NUM>. Furthermore, said tightening member <NUM> comprises at least one manoeuvring portion <NUM> which is arranged in an offset relation relative to the joint <NUM>, when looking axially towards the differential unit <NUM>. As a consequence, the tightening member manoeuvring portion <NUM> is visible and accessible despite the joint <NUM>, at least during a tightening phase of the mounting process of the axle system <NUM>.

For example, the tightening member <NUM> can be configured to axially tighten the first bearing outer ring <NUM> against a radial wall <NUM> of the first housing <NUM>. In practice, the first housing <NUM> can form substantially a sleeve around axis <NUM>, provided with an inwardly projecting rib forming said radial wall <NUM>.

In the embodiment shown in <FIG>, the tightening member <NUM> comprises a nut. As best seen in <FIG>, the tightening member <NUM> has an axis <NUM>. It comprises a tightening portion <NUM>, which may be formed as a sleeve coaxial with the drive shaft <NUM> in use and which is configured for abutting against the outer ring <NUM> of the first bearing <NUM>. The tightening portion <NUM> may have an outer thread (not shown) for cooperating with an inner thread of the first housing <NUM>. The tightening member <NUM> also comprises an outer annular flange <NUM>. The flange <NUM> comprises at least one notch <NUM> which opens outwardly and which forms one manoeuvring portion. Preferably, the flange <NUM> comprises several notches <NUM> regularly circumferentially spaced, forming a crenulated peripheral area A. Alternatively, the notch or notches <NUM> could open axially.

As shown in <FIG>, the peripheral area A including the notches <NUM> has at least an outer diameter D51 that is larger than the radial dimension D of the joint <NUM>, and preferably also an inner diameter that is larger than the radial dimension D of the joint <NUM>.

Thus, the notches <NUM> - i.e. the manoeuvring portions of the tightening member <NUM> - are located in an area A of the tightening member <NUM> which is radially outwardly offset from the joint <NUM>, when looking axially towards the differential unit <NUM>, or at least partially radially outwardly offset. The notches <NUM> can therefore receive a tool capable of moving the tightening member <NUM> axially relative to the first housing <NUM>.

The axle system may comprise a contact piece <NUM> secured around the drive shaft <NUM>. Said contact piece <NUM> forms an intermediate piece between the inner ring <NUM> and the shoulder <NUM> as previously described.

The contact piece <NUM> has a blocking portion <NUM> which may be formed as a sleeve coaxial with the drive shaft <NUM>, and which is configured for abutting against the inner ring <NUM> of the first bearing <NUM>. The first bearing inner ring <NUM> is therefore tightened between the contact piece blocking portion <NUM> and the nut <NUM>.

The contact piece <NUM> also has a contact portion <NUM> such as a cylindrical contact portion coaxial with the drive shaft <NUM>. The contact portion <NUM> is arranged not to hide, or not to fully hide, the manoeuvring portion(s) <NUM>, when looking axially towards the differential unit <NUM>, in order to allow access to said manoeuvring portion(s) <NUM>, for tightening the first bearing outer ring <NUM> against the first housing <NUM>. For that purpose, the contact portion <NUM> preferably has an outer diameter D62 that is less than the outer diameter D51 of the tightening member peripheral area A. The contact portion <NUM> can be fully radially inwardly offset relative to the tightening member manoeuvring portion <NUM>, or only partially offset, i.e. partly facing the peripheral area A along the longitudinal direction X, as shown in <FIG>.

In the mounted position, the axle system <NUM> also comprises an annular cover <NUM> having a central opening <NUM> for receiving the drive shaft <NUM>. The annular cover <NUM> is removably fastened to the second housing <NUM> by means of appropriate fasteners <NUM> (see <FIG> and <FIG>).

An annular seal <NUM> is mounted in the central opening <NUM> of the annular cover <NUM> and is in contact with the contact portion <NUM> of the contact piece <NUM>. In other words, the annular seal <NUM> is arranged between the contact piece <NUM> - secured to the drive shaft <NUM> - and the annular cover <NUM> - secured to the second housing <NUM>. In this embodiment, the annular seal <NUM> can have an inner diameter (i.e. where the contact with the opposite piece occurs) that is larger than the radial dimension D of the joint <NUM> (in other words, D62 > D). This makes it possible to change the annular seal <NUM> when needed, for maintenance operations during the service life of the axle system <NUM>, without requiring the drive shaft <NUM> to be removed from the differential unit <NUM>. This also avoids damaging the annular seal <NUM> when the drive shaft <NUM> is mounted.

A mounting process of the axle system will now be described, with reference to <FIG>.

As shown in <FIG>, the differential unit <NUM> is prepared, with the differential <NUM>, the first housing <NUM>, the second bearings <NUM> (on either side of the joint cross <NUM>), and possibly the blocking system <NUM>. Then, as shown in <FIG>, the assembly of <FIG> is inserted in the second housing <NUM>. Differential nuts <NUM> are tightened to set the bevel set backlash and the preload of the second bearings <NUM>.

Two drive shaft sub-assemblies <NUM> are also prepared.

A shown in <FIG>, one drive shaft sub-assembly <NUM> comprises a drive shaft <NUM> including at least one joint <NUM> between the first portion 114a configured to be connected to the differential unit <NUM> and an intermediate portion 114d. The drive shaft sub-assembly <NUM> also includes:.

Then the annular seal <NUM> is mounted in the central opening <NUM> of the annular cover <NUM>, for both covers <NUM>. This step is not illustrated.

The drive shaft sub-assembly <NUM> is then engaged in the assembly illustrated in <FIG>, in the first housing <NUM>, in order to connect the drive shaft <NUM> to the differential unit <NUM>, i.e. to insert the end of the drive shaft first portion 114a into the corresponding differential side gear <NUM> and to rotationally link the first portion 114a and the differential side gear <NUM>. The first bearing <NUM> is thus placed between the drive shaft <NUM> and the first housing <NUM>, as illustrated in <FIG>.

At this stage of the mounting process, the axle system <NUM> is as illustrated in <FIG> and <FIG>. It can be seen that the first bearing <NUM> is not visible, because of its small diameter D30. On the contrary, the tightening member <NUM> is not fully hidden, as its manoeuvring portion(s) <NUM> are radially located outward from the contact piece <NUM> and the joint <NUM>, and inward from the differential nut <NUM>. The manoeuvring portion(s) <NUM> being visible and accessible by an operator, the tightening member <NUM> can thus be operated, during a tightening phase of the axle system mounting process. In practice, a tool can be introduced in the notches <NUM> in order to rigidly secure (i.e. without play) the first bearing outer ring <NUM> relative to the first housing <NUM>.

The tightening member <NUM> is thus a partly external piece - at least during the tightening phase - which makes it possible to ensure tightening while the drive shaft <NUM> has already been mounted.

Once the first bearing <NUM> has been properly axially locked, the annular cover <NUM> equipped with the annular seal <NUM> can be mounted, by being engaged around the drive shaft <NUM> (on both sides of the second housing <NUM>). In the mounted position, illustrated in <FIG>, <FIG> <FIG> and <FIG>, the annular seal <NUM> is in contact with the outer face of the contact piece contact portion <NUM>, and the annular cover <NUM> is fastened to the second housing <NUM> by the fasteners <NUM>.

In <FIG>, the annular cover <NUM> is represented as a transparent piece, only its edge being illustrated with a dotted line. It can thus be seen that the tightening member manoeuvring portions <NUM> are not visible any more, as they are hidden by the annular seal <NUM>, when looking axially towards the differential unit <NUM>.

The annular cover <NUM> may comprise at least one pin (not shown) protruding axially towards the differential <NUM> and configured to engage the differential nut <NUM>, preferably the inner part thereof, to prevent rotation i.e. untightening of said differential nut <NUM>.

A variant of the first embodiment is illustrated in <FIG>.

In this variant, there is not provided a mechanical differential. Rather, the differential effect is achieved by the fact that the wheels are driven independently by a dedicated motor and corresponding transmission system, in a so-called torque vectoring technology. In <FIG>, the motor is electric, however, other kinds of motors could be envisaged, such as a hydraulic motor.

The driven wheel system <NUM> comprises one powertrain module <NUM> for rotating one drive shaft <NUM> and another powertrain module <NUM> for rotating the other drive shaft <NUM>. One powertrain module <NUM> comprises a casing <NUM> and a powertrain system which is configured to drive the drive shaft <NUM>, and which comprises:.

In an embodiment, the transmission system may comprise a first epicyclic gear train <NUM> having a first axis A100, and a second epicyclic gear train <NUM> having a second axis A200 which is parallel to the first axis A100. In the operating position, i.e. when the powertrain module <NUM> is mounted on the vehicle <NUM>, the axes A100 and A200 are parallel to direction Y'. In a variant, the first epicyclic gear train <NUM> may be omitted and replaced by a more conventional parallel gear train reduction arrangement.

The first epicyclic gear train <NUM> can comprise:.

The second epicyclic gear train <NUM> can comprise:.

A first bearing <NUM> is mounted between the drive shaft <NUM> and the casing <NUM>, while a second bearing <NUM> is mounted between the casing <NUM> and the hub <NUM>. A tightening member <NUM> having an accessible manoeuvring portion <NUM>, at least during a tightening phase of the mounting process, is provided to axially lock the first bearing outer ring <NUM> relative to the casing <NUM>.

Reference is now made to <FIG> which show a second embodiment of the invention.

The axle system <NUM> may be devoid of a contact piece <NUM> as previously described. Rather, the drive shaft <NUM> - more specifically the first portion 114a - may comprise a stepped portion including a transverse face or shoulder <NUM> which forms an axial abutment for the first bearing <NUM> and a cylindrical face which forms a contact portion <NUM> with which the annular seal <NUM> is in contact in use.

The diameter of the cylindrical face <NUM> can be less than the radial dimension D of the joint <NUM>, which means that the annular seal <NUM> has an inner diameter that is smaller than the radial dimension D of the joint <NUM>. Besides, the diameter of the cylindrical face <NUM> is preferably larger than the first bearing inner diameter.

The mounting process of the axle system will now be described.

Two drive shaft sub-assemblies <NUM> are prepared as shown in <FIG>.

One drive shaft sub-assembly <NUM> comprises a drive shaft <NUM> including at least one joint <NUM> between the first portion 114a configured to be connected to the differential unit <NUM> and an intermediate portion 114d. The drive shaft sub-assembly <NUM> also includes:.

A bearing rotation lock <NUM> can further be provided on the side of the first bearing <NUM> that is opposite the annular cover <NUM>, i.e. towards the inside of the differential unit <NUM>.

The annular cover <NUM> comprises at least one aperture <NUM> (see <FIG>), preferably several apertures <NUM> arranged substantially on one and the same circle around axis <NUM>. When looking axially towards the differential unit <NUM>, the apertures <NUM> are located in an area A74 which is at least partially included in the joint enveloping cylinder C. However, the annular cover <NUM> is placed or can be placed around the drive shaft <NUM> so that the apertures <NUM> are in a circumferentially offset position from the joint <NUM>, i.e. in a circumferentially offset position from both U-shaped pieces <NUM>, <NUM>.

The differential unit <NUM> is also prepared, with the differential <NUM>, the first housing <NUM>, the second bearings <NUM> (on either side of the joint cross <NUM>), and possibly the blocking system <NUM>.

Then, as shown in <FIG>, the drive shaft sub-assembly <NUM> of <FIG> is inserted in the differential unit <NUM>,
The drive shaft sub-assembly <NUM> is then engaged in the assembly illustrated in <FIG>, in the first housing <NUM>, in order to connect the drive shaft <NUM> to the differential unit <NUM>, i.e. to insert the end of the drive shaft first portion 114a into the corresponding differential side gear <NUM> and to rotationally link the first portion 114a and the differential side gear <NUM>. The first bearing <NUM> is thus placed between the drive shaft <NUM> and the first housing <NUM>.

The engagement of the drive shaft <NUM> can continue until the first bearing <NUM> abuts against the first housing <NUM>, as illustrated in <FIG>.

Then, the tightening phase of the first bearing outer ring <NUM> can be carried out, in order to axially lock the first bearing outer ring <NUM> relative to the first housing <NUM>. To that end, in this embodiment, there are provided at least one tightening member <NUM> as a separate piece.

One tightening member <NUM> may comprise a plate configured for abutting against the outer ring <NUM> of the first bearing <NUM>. The plate can be substantially flat. It is designed to be inserted through one aperture <NUM> of the annular cover <NUM>, and therefore is dimensioned appropriately. Each plate <NUM> comprises at least one hole, and preferably at least two holes, which form a manoeuvring portion <NUM> of the tightening member <NUM>, as a tool can be engaged in the hole <NUM> to move the plate <NUM> axially relative to the first housing <NUM>.

There are preferably provided several tightening members <NUM>, preferably one for each aperture <NUM>.

In other words, in this embodiment, the tightening members <NUM> are arranged substantially on one and the same circle. Moreover, when looking axially towards the differential unit <NUM>, the manoeuvring portions <NUM> are located in an area A74 at least partially included in the joint enveloping cylinder C but are circumferentially offset from the U-shaped pieces <NUM>, <NUM> of the joint <NUM>.

Then one tightening member, i.e. one plate <NUM>, is inserted through several or each aperture <NUM>, until it abuts against the outer ring <NUM> of the first bearing <NUM>, as shown in <FIG>. The aperture <NUM> axially facing the tightening member <NUM>, it allows access to the holes <NUM>, i.e. the manoeuvring portions. The bearing <NUM> can thus be properly axially locked.

The annular cover <NUM> can then be removably plugged or fastened to the second housing <NUM>, by means of the fasteners <NUM>. The annular seal <NUM> is thus arranged between the drive shaft <NUM> and the annular cover <NUM> secured to the second housing <NUM>.

Although this second embodiment has been described with a mechanical differential, it could be implemented with a torque vectoring solution.

The invention applies to vehicles having an independent wheel suspension arrangement in which, for mechanical strength reasons, for providing enough space to allow operational movements of the components, and for improving fuel efficiency, the drive shafts must have a minimum length that may not be easily compatible with the legal constraints, namely the regulatory maximum transverse length of the vehicle.

In this context, the invention gives a solution for providing an axle system which offers both stronger support for the drive shafts, because of the first and second bearings, and robustness, as axial blocking is achieved without play which avoid relative movements and resulting components wear.

Moreover, the mutual arrangement of the bearings offers the required compactness, especially in the transverse direction of the vehicle.

Besides, the invention allows easing maintenance on the drive shafts, which can be disassembled without disassembling the differential (as disassembling the drive shafts occurs at an early stage of the disassembling process), and also easing maintenance on the seal, as it can be quickly changed, at least in the first embodiment.

The invention advantages are all the more significant as independent wheel suspension configuration is a key solution to develop an optimized electrified driveline, which is a promising development in transportation industry.

Claim 1:
An axle system (<NUM>) for a vehicle (<NUM>), having an axis (<NUM>) and comprising:
- a differential unit (<NUM>) including a first housing (<NUM>) and a second housing (<NUM>) which is at least partially arranged around the first housing (<NUM>) and which rotationally receives at least part of said first housing (<NUM>);
- at least one drive shaft (<NUM>) having one end (<NUM>) configured to be connected to a wheel (<NUM>) of the vehicle (<NUM>) and one end (<NUM>) connected to the differential unit (<NUM>) and rotationally received in the first housing (<NUM>), the drive shaft (<NUM>) including at least one joint (<NUM>) connecting two portions (114a-d) of the drive shaft (<NUM>) to transmit rotary motion between said portions (114a-d), the joint (<NUM>) having a radial dimension (D);
- a first bearing (<NUM>) placed between the drive shaft (<NUM>) and the first housing (<NUM>), the first bearing (<NUM>) having an inner ring (<NUM>) secured around the drive shaft (<NUM>) and an outer ring (<NUM>);
- a second bearing (<NUM>) placed between the first housing (<NUM>) and the second housing (<NUM>);
characterized in that:
- the outer diameter (D30) of the first bearing (<NUM>) is smaller than the radial dimension (D) of the joint (<NUM>);
- and the axle system (<NUM>) comprises at least one tightening member (<NUM>) configured to axially lock the first bearing outer ring (<NUM>) relative to the first housing (<NUM>), said tightening member (<NUM>) comprising at least one manoeuvring portion (<NUM>) which is arranged in an offset relation relative to the joint (<NUM>), when looking axially towards the differential unit (<NUM>), so that the tightening member manoeuvring portion (<NUM>) is visible and accessible, at least during a tightening phase of an axle system mounting process.