Assembly for a differential unit of a vehicle

The invention relates to an assembly for a differential unit of a vehicle, the assembly comprising: —a first housing portion (20a) designed to be assembled with a second housing portion for forming a differential carrier housing; —a first and a second supporting devices (30, 301, 302), each comprising a main portion (33) having substantially the shape of a ring and a base portion (31) attached to the first housing portion (20a) so that the main portions (33) of the first and second supporting devices (30) are substantially coaxial along a longitudinal direction (X), the first and second supporting devices being configured to support, in use, a system comprising a crown wheel (22) and a differential housing (24) containing a differential, the system having two end portions each including a bearing which has an inner ring (51) mounted on the differential housing (24), an outer ring configured to be mounted in the main portion (33) of one of the supporting devices (30), and rolling elements. The first housing portion (20a), the first supporting device (301) and the second supporting device (302) are made as a single piece. Moreover, the main portion (33) of at least one supporting device (30) comprises a notch (40) for inserting at least part of a corresponding end portion of the system (100), the notch (40) opening: —in a radial direction (Y), which is orthogonal to the longitudinal direction (X); —and in the longitudinal direction (X), towards the opposite supporting device (30).

This application is a 35 USC 371 national phase filing of International Application No. PCT/IB2016/001913, filed Dec. 7, 2016, the disclosure of which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The invention relates to an assembly for a differential unit of a vehicle. The invention also relates to a differential unit comprising such an assembly, to an axle comprising such a differential unit, to a vehicle comprising such an axle, and to a method for mounting a differential unit.

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

BACKGROUND

A vehicle such as a truck is generally equipped with one or several differential units on its driven axles.

A differential unit typically comprises a differential carrier housing which is made of a first housing portion assembled with a second housing portion, and which contains the differential mechanism, i.e.: a crown wheel driven by an input shaft, a differential arranged inside the crown wheel and comprising pinions and gears, and a differential housing containing the differential and part of drive shafts connected to a wheel of the vehicle.

The differential housing is rotatably mounted in the differential carrier housing. To that end, the first housing portion comprises a first and a second supporting devices each comprising a main portion having substantially the shape of a ring, for receiving a bearing mounted around the differential housing surrounding the drive shaft.

According to a known implementation, a supporting device is made of a first half ring which is made as a single piece with the first housing portion, and a second half ring which is manufactured as a separate piece and subsequently secured to the first half ring.

This implementation has several drawbacks. In particular, it requires manufacturing and assembling several parts, which is unfavourable in terms of time and cost. Besides, the half rings needs to be paired after they have been machined together in the assembled position, to ensure proper operation of the differential unit. Moreover, having a supporting device made of two separate parts may lead to the ring being less resistance to mechanical fatigue and becoming oval over time, which would result in a malfunctioning of the differential unit.

According to another known implementation, the supporting devices are made of as a single piece with the first housing portion. With such an implementation, mounting the differential mechanism between the supporting devices with the end portions of the differential housing engaged in the supporting devices is fairly complicated. Indeed, this requires to first engage one end portion of the differential housing in one supporting device, with the differential mechanism being arranged obliquely, and then to move the differential mechanism towards a straight position in order to engage the other end portion of the differential housing in the other supporting device. In other words, the mounting process requires a combination of successive movements of the differential mechanism, which are not easy to perform, all the more as the differential mechanism can be heavy. Thus, this implementation proves difficult to mount by an operator. Another drawback of this implementation is that the successive movements of the differential mechanism require a great space to be performed, resulting in a differential unit having a large size.

SUMMARY

An object of the invention is to provide an improved differential unit for a vehicle.

More specifically, an object of the invention is to provide a differential unit for a vehicle which is advantageous as compared to the prior art in terms of manufacturing process, durability and mounting process.

To that end, and according to a first aspect, the invention concerns an assembly for a differential unit of a vehicle, the assembly comprising:a first housing portion designed to be assembled with a second housing portion for forming a differential carrier housing;a first and a second supporting devices, each comprising a main portion having substantially the shape of a ring and a base portion attached to the first housing portion so that the main portions of the first and second supporting devices are substantially coaxial along a longitudinal direction, the first and second supporting devices being configured to support, in use, a system comprising a crown wheel and a differential housing containing a differential, the system having two end portions each including a bearing which has an inner ring arranged around the differential housing, an outer ring configured to be mounted in the main portion of one of the supporting devices, and rolling elements;

wherein the first housing portion, the first supporting device and the second supporting device are made as a single piece, and in that the main portion of at least one supporting device comprises a notch for inserting at least part of a corresponding end portion of the system, the notch opening:in a radial direction, which is orthogonal to the longitudinal direction; andin the longitudinal direction, towards the opposite supporting device.

More specifically said notch forms a through hole in the radial direction and preferably a non-through hole in the longitudinal direction.

Said inner ring arranged around the differential housing can be a ring mounted on the differential housing. Alternatively, said inner ring can be integral with the differential housing. In other words, in the latter case, each inner ring can be made as a single piece with a differential housing part.

Preferably, each supporting device comprises a notch for inserting at least part of the corresponding end portions of the system and the notches are substantially facing each other along the longitudinal direction.

In the longitudinal direction said notch forms a non-through hole and comprises therefore according to the longitudinal direction a bottom. If both supporting devices comprise a notch for inserting at least part of the end portions of the system, the bottoms of the notches are preferably separated from each other by a distance, according to the longitudinal direction, that is greater than the length of the system between its two end portions.

If only one supporting device comprises a notch for inserting at least part of the corresponding end portion of the system, the bottom of said notch is separated from the other supporting device by a distance, according to the longitudinal direction, that is greater than the length of the system between its two end portions.

Because the first housing portion, the first supporting device and the second supporting device are made as a single piece, the invention provides an assembly which has numerous advantages: by reducing the number of constituting parts to only one, the assembly is less expensive to manufacture and the logistics is simplified; insofar as no assembling step is to be performed, costs are further reduced, there is no need to provide fasteners to assemble the various constituting parts, and no parts pairing is required; the overall stiffness is increased as compared to an assembly made of separate parts secured the ones to the others, which is of particular interest for the bevel set gears contact and improves durability.

Moreover, owing to said one or both notches, such a “one-piece” configuration does not complicate the mounting process. Indeed, if each supporting device comprises a notch for inserting at least part of the corresponding end portions of the system, mounting the system on the assembly requires only a translation movement of the system towards the supporting devices, along the above-mentioned radial direction. If only one supporting device comprises a notch, mounting the system on the assembly requires a first translation movement of the system towards the supporting devices, along the above-mentioned radial direction and may require a further second translation movement along the longitudinal direction. This simple movement or sequence of two movements can be easily performed by an operator. It can be envisaged that, during the mounting operations, the only one movement or the first movement is a downward translation, which is even easier to perform. Furthermore, no specific space is required to perform this movement and, consequently, the differential unit can be fairly compact.

Said notch can be arranged on said at least one supporting device substantially opposite the base portion with respect to the longitudinal axis. Then, mounting the system on the assembly can be therefore performed by only one translation movement of the system in the transverse direction, i.e. towards the first housing portion. If only one notch is provided, this first translation movement is preferably followed by a second translation movement along the longitudinal direction. This makes the assembly easier because a large access is provided to the assembly.

According to an implementation, said at least one notch is dimensioned to allow mounting the system when it is devoid of the bearing outer rings—and preferably also devoid of the rolling elements and possible cage receiving said rolling elements—and the assembly is configured to prevent movement of the whole system—i.e. the system including the bearings in their entirety, including the outer rings—out of said notch once the system has been mounted in the supporting devices. For example, said or each notch can form an opening in the ring-shaped main portion of the supporting device, the width of said opening being greater than the outer diameter of the bearing inner ring.

Alternatively, said at least one notch could be dimensioned to allow inserting the whole system, with an additional mean being provided for subsequently prevent the whole system from moving out of said notch.

Said at least one notch can further be dimensioned to prevent movement of the whole system out of said notch. With this implementation, the outer ring of the bearing forms a means for at least partially closing the notch. For example, the notch or each notch forms an opening in the ring-shaped main portion of the supporting device, the width of said opening being less than the outer diameter of the bearing outer ring.

Alternatively or in addition, the assembly may further comprise at least one cover which can be assembled to one supporting device in order to at least partially close said at least one notch so as to prevent movement of the whole system out of said at least one notch once the system has been mounted in the supporting devices.

According to a second aspect, the invention concerns a differential unit comprising an assembly as previously described and, mounted on said assembly:a differential comprising differential side pinions fitted on a joint cross of the differential and two differential side gears each connected to at least one differential side pinion and to a drive shaft capable of being connected to at least one wheel of a vehicle, outside the differential carrier housing;a differential housing containing the differential and a part of the drive shafts,a crown wheel having a longitudinal axis, the crown wheel being arranged to be driven in rotation around said longitudinal axis by an input shaft, the crown wheel being connected to the joint cross of the differential in a rotationally fixed manner, the crown wheel being secured to the differential housing and the crown wheel being arranged substantially around the differential housing;on both sides of the crown wheel, a bearing having an inner ring arranged around the differential housing, rolling elements, and an outer ring mounted in the ring-shaped main portion of the corresponding supporting device.

In an implementation, the or each notch defines an opening in the ring-shaped main portion of the corresponding supporting device, the width of said opening being greater than the outer diameter of the bearing inner ring. Therefore, the or each notch allows mounting the system when the inner rings are present.

For example, the or each notch can define an opening in the ring-shaped main portion of the corresponding supporting device, the width of said opening being less than the outer diameter of the bearing outer ring. Then, the or each notch allows mounting the system only when the outer rings are not present, and prevent the system including the outer rings from moving out of the or each notch, i.e. out of the supporting devices, once it is mounted on the assembly.

With this implementation, the outer ring of the bearing forms a means for at least partially closing the notch. Alternatively, for example if each or the notch is larger, it may be provided a separate cover to close the notch and thus lock the system in the mounted position.

According to a third aspect, the invention relates to an axle comprising a differential unit as previously described, the axle comprising an axle housing which forms the second housing portion designed to be assembled to the first housing portion and which contains the drive shafts, the axle further comprising a wheel connected to one end of each drive shaft.

According to a fourth aspect, the invention relates to a vehicle comprising at least one axle as previously described.

According to a fifth aspect, the invention relates to a method for mounting a differential unit, the method comprising:a) providing an assembly as previously described;b) providing a system comprising a crown wheel and a differential housing containing a differential, the system having two end portions each including a bearing which has an inner ring arranged around the differential housing, an outer ring, and rolling elements;c) inserting at least part of at least one end portion of the system through at least one notch of the first and/or second supporting devices, along said radial direction, in order to mount the system on the assembly.

In other words, the system is mounted between the supporting devices, with the end portions of the differential housing engaged in the supporting devices, by at least one translation movement of the system along the radial direction defined by said at least one notch.

Preferably in step a) of the method each supporting device comprises a notch for inserting at least part of the corresponding end portions of the system and the notches are substantially facing each other along the longitudinal direction; and in step c) of the method at least part of each end portion of the system is inserted through the notch of each of the first and second supporting devices, along said radial direction, in order to mount the system on the assembly.

In other words, the system is mounted between the supporting devices, with the end portions of the differential housing engaged in the supporting devices, by a translation movement of the system along the radial direction defined by the two notches of both supporting devices, which is a movement easy to perform.

In an implementation, the method comprises mounting the system devoid of the bearing outer rings on the assembly, and preferably further devoid of rolling elements and cage.

Then, once the system devoid of the bearing outer rings is mounted on the assembly, the method can comprise inserting each bearing outer ring around the corresponding bearing inner ring and inside the ring-shaped main portion of the corresponding supporting device, along the longitudinal direction, towards the opposite supporting device.

The method may further comprise closing said notch, after step c). The notch can be closed by a separate cover assembled to the supporting device, or by the outer ring of the bearing.

Once the system is mounted on the assembly, the method may comprise assembling a nut on each end portion of the system, generally along the longitudinal direction and towards the opposite supporting device, the nut having an outer thread for cooperating with an inner thread of the ring-shaped main portion of each supporting device, and a central hole for engagement around the differential housing. Such a nut can typically be used to axially press the outer ring of the corresponding bearing.

Once the nuts are mounted, the method may comprise inserting an end portion of a drive shaft in the differential housing, along the longitudinal direction and towards the opposite supporting device. In practice, a drive shaft is inserted in the differential housing on both sides of the crown wheel.

As shown inFIG. 1, a vehicle1comprises an engine2that drives an input shaft3having an axis13, and a front axle4connected to front wheels5.

The vehicle1also comprises at least one rear axle6. The or each rear axle6comprises an axle housing7containing a differential unit10, which includes a differential15, and two drive shafts11. Each drive shaft11has a first end connected to the differential15and a second end connected to at least one wheel8. In the illustrated embodiment, the vehicle1comprises a first driven rear axle6aand a second driven rear axle6blocated rearwards from the first driven rear axle6a, each rear axle6a,6bcomprising two wheels8on either side. An additional shaft9connects the input shaft3to the differential unit10of the second driven rear axle6b, through the differential unit10of the first driven rear axle6a, and is the input shaft for the differential unit10of the second driven rear axle6b.

With reference toFIGS. 2 and 3, the differential unit10comprises a differential carrier housing20.

The differential carrier housing20is made of a first housing portion20ashown inFIGS. 2 and 3, and a second housing portion which can be formed by the axle housing7, the first and second housing portions being secured to one another by means of appropriate fasteners (not shown). For example, the housing portions can substantially form half shells secured along their peripheral edge by bolts inserted in holes27. Except inFIG. 1, only the first housing portion20aof the differential carrier housing20has been illustrated, so that the inside of said differential carrier housing20can be seen.

Inside the differential carrier housing20is located a crown wheel22having a longitudinal axis23. The crown wheel22is driven in rotation around said longitudinal axis23by the input shaft3, by engagement of teeth arranged on a pinion12mounted on said input shaft3and teeth arranged on the crown wheel22(the teeth are not illustrated).

As shown inFIG. 2, the longitudinal direction X is defined as a direction parallel to the longitudinal axis23of the crown wheel22. In the operating position, i.e. when the differential unit is mounted under the vehicle1, as shown inFIG. 1, the longitudinal direction X corresponds the transverse direction Y′ of the vehicle1, i.e. the direction of the axles4,6. Direction X is substantially horizontal when the vehicle1is 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 vehicle1is on a horizontal surface. Direction Y corresponds the longitudinal direction X′ of the vehicle1. The axis13of the input shaft3is parallel to the transverse direction Y, i.e the longitudinal direction X′ of the vehicle1.

Moreover, direction Z is defined as the vertical direction—when the vehicle1is on a horizontal surface.

The invention will be described when the vehicle1is on a horizontal surface.

Inside the crown wheel22is arranged a differential15which comprises differential side pinions16, for example four differential side pinions, which are fitted on a joint cross17connected to the crown wheel22, and two differential side gears18. Each differential side gear18meshes with at least one differential side pinion16and is fastened to a first end of one of the drive shafts11.

The differential unit10further comprises, inside the differential carrier housing20, a differential housing24which contains the differential15and part of the drive shafts11, namely the part of each drive shaft11which is located near the first end of said drive shaft11. The crown wheel22is secured to the differential housing24. The differential housing24may be made of two parts24a,24beach forming a sleeve around the corresponding drive shaft11, said parts24a,24bcan be, for instance, fastened on both sides of the crown wheel22.

The crown wheel22, differential15, and differential housing24are rotating parts inside and with respect to the differential carrier housing20. They are mounted on the inner side of the differential carrier housing20by means of two supporting devices30. Each supporting device30is attached to the first housing portion20aand carries a bearing50having an inner ring51that is mounted on the differential housing24,24a,24band an outer ring52mounted on the supporting device30. Each bearing50further comprises rolling elements53arranged in a cage54(seeFIG. 9for example). The supporting devices30are located on both sides of the crown wheel22. The bearings50are preferably conical bearings. Alternatively, said inner ring51can be integral with the differential housing24,24a,24b, in other words each inner ring51can alternatively be made as a single piece with a differential housing part24aor24b.

The supporting devices30are located on both sides of the crown wheel22. More precisely, there is provided a first supporting device301and a second support device302, the second support device302being located on the same side of the crown wheel22as the input shaft3.

Each supporting device30comprises a main portion33which is substantially in the shape of a ring, and a base portion31attached to the first housing portion20aso that the main portions33of the first and second supporting devices are substantially coaxial along the longitudinal axis23, i.e. along the longitudinal direction X. The base portion31can have the shape of a substantially rectangular plate. One or several reinforcing walls may be provided on a supporting device30, for example between the ring-shaped main portion33and the base31. Each main portion33forms a circular opening34in which is mounted the outer ring52of the bearing50.

In other words, the supporting devices30are configured to support, in use, a system100comprising the crown wheel22, the differential housing24containing the differential15, and the bearings50mounted at the end portions of the system (as shown onFIG. 11).

In use, the housing20contains a lubricant bath in which the crown wheel22soaks. When the crown wheel22is rotated, it projects lubricant from the bath inside the housing thanks to its teeth. Part of this projected lubricant directly contacts some constituents and therefore lubricate them. Another part of this projected lubricant can be collected by a collector35arranged on one of the supporting devices30. In the disclosed embodiment, the collector35is arranged on the second supporting device302.

The collector35can have a substantially rectangular and planar bottom wall which is substantially horizontal in use, a peripheral wall and an open upper surface. As shown onFIG. 2, the collector35can extend in the longitudinal direction X from the main portion33of the second supporting device302, towards the differential15, in use.

The collector35can be offset with respect to the longitudinal axis23, for example both along the Y axis and the Z axis. More specifically, the collector35can be located on the second supporting device302near to the base31, and preferably above the longitudinal axis23, in order to take advantage of gravity.

The bottom wall of the collector35includes a through hole37. Moreover, specific arrangements can allow the collected lubricant flowing through the hole37to be directed to the differential15, the constituents of which (especially the differential side pinions16and differential side gears18) cannot be reached easily by the projected lubricant.

As can be seen on the figures, the first housing portion20aand the two supporting devices30are made as a single piece. In other words, they are not made of several parts secured to one another. For example, the first housing portion20aand the two supporting devices30are made together by casting of a metal.

Furthermore, the main portion33of each supporting device30comprises a notch40for allowing mounting the system on the assembly comprising the first housing portion20aand the supporting devices30. More specifically, the notch40allows inserting at least part of the corresponding end portion of the system.

The notches40substantially face each other along the longitudinal direction X. They are preferably arranged on the supporting devices30opposite the base portion31.

Each notch40opens in a radial direction—which is orthogonal to the longitudinal direction X—on both sides of the main portion, i.e. towards the axis23and towards the outside of the main portion33. In the illustrated embodiment, as the notches40are arranged opposite the base portion31, said radial direction is the transverse direction Y. However, other implementations can be envisaged. Furthermore, each notch40opens in the longitudinal direction X towards the opposite supporting device30.

As shown onFIGS. 2 and 4, each notch40can comprise a bottom face41which is substantially parallel to a plane (Y,Z), and two sides faces42which are substantially parallel to a plane (X,Y). The distance D between the side faces42is the width of each notch40of the supporting device30(seeFIGS. 7, 8 and 10).

In an embodiment of the invention, the distance D can be greater than the outer diameter d51of the bearing inner ring51, and less than the outer diameter d52of the bearing outer ring52(seeFIGS. 8 and 10). In the embodiment illustrated, where the bearing50is conical, it is specified that the term “diameter” refers to the higher diameter of the bearing inner ring51or outer ring52.

Thus, the system100′ provided with the bearing inner rings51, but devoid of the bearing outer rings52(and preferably also devoid of the rolling elements53and cage54) can be moved according to arrow A1(seeFIG. 6), along the transverse direction Y, so that the inner rings51pass through the notches40, as illustrated inFIG. 6.

Before this mounting step and when the bearing inner ring51is a mounted part and not made as a single piece with a differential housing part24aor24b, a bearing inner ring51has been preliminarily mounted on each of the parts24a,24bof the differential housing24, said parts24a,24bcan be fastened on both sides of the crown wheel22, as illustrated inFIG. 5.

As can be seen onFIGS. 4 and 7, given the distance between the supporting devices301,302, the height h of the notches40—along the longitudinal direction X—is great enough to allow the differential housing24to be inserted between the bottom faces41of the notches40.

Subsequently, as shown onFIG. 9, each bearing outer ring52(as well as the rolling elements53and cage54if they were not mounted yet) is mounted around the corresponding bearing inner ring51by being inserted inside the ring-shaped main portion33of the corresponding supporting device30. This is performed by a movement according to arrows A2, along the longitudinal direction X, towards the opposite supporting device30.

Then, because D is less than d52, as explained above and as shown inFIG. 10, the whole system cannot move out of the notches40, i.e. out of the supporting devices30. With this implementation, the bearing outer rings52form a means at least partially closing the notches40.

In a subsequent step of the mounting process, a nut60is preferably assembled on each end portion of the system, as shown onFIG. 11.

The nut60has an outer thread (not shown), for cooperating with an inner thread (not shown) of the ring-shaped main portion33of each supporting device30, and a central hole61for engagement around the differential housing24. Each nut60is assembled generally along the longitudinal direction X, while simultaneously being threaded, and towards the opposite supporting device30.

In practice, after this step, the bearing50is arranged around the differential housing24, the inner ring51resting against a radial shoulder25arranged on the differential housing24, and facing opposite the differential15. Moreover, the nut60is mounted in the circular opening34of the supporting device30, on the side of the bearing50which is opposite the radial shoulder25. The nut60is threaded with respect to the circular opening34, i.e. rotated, so as to provide an appropriate preload—i.e. axial pressure—on the outer ring52of the bearing50. In other words, the bearing50is pushed against the shoulder25by the nut60.

At this stage, the system is properly mounted and locked in the operative position. Furthermore, the inter wheel differential bearing preload and the bevel set backlash have been adjusted. The nuts60can then be maintained in this position by means of appropriate fasteners45inserted through holes44of the supporting device30.

The inner thread of the ring-shaped main portion33, for cooperating with the nut60, can only be made when the ring is actually formed. Because each supporting device30of the invention is made as a single piece, the process does not include:a preliminary step for mounting several parts to one another to form the ring-shaped main portion33; anda pairing of parts to ensure that the parts which will be secured to one another to form the supporting device30were threaded together, to avoid malfunctioning of the differential unit10.

Therefore, the invention provides an improved differential unit in terms of manufacturing and mounting process, reliability and robustness.

The differential unit10is then ready to be assembled to the axle housing7.

The method then comprises inserting an end portion of a drive shaft11in each part24a,24bof the differential housing24, along the longitudinal direction X and towards the opposite supporting device30, in order to form the rear axle6(seeFIG. 12).

For instances, onFIGS. 2 to 12illustrating embodiments previously described, each supporting device comprises a notch40. In a variant only one of the supporting device can be provided with a notch.

According to the latter variant, the system100′ provided with the bearing inner rings51, but devoid of the bearing outer rings52(and preferably also devoid of the rolling elements53and cage54) can be firstly moved along the transverse direction Y, so that a first end portion of the system100′ and the corresponding first inner ring51pass through the notch of a first supporting device30and then can be further moved along the longitudinal direction X towards the second supporting device30so that the second end portion of the systems100′ and the corresponding second inner ring51are introduced into the main portion of the second supporting device30.