Wheel hub arrangement for a driving wheel of a vehicle

A wheel hub arrangement for a driving wheel of a vehicle is provided. The wheel hub arrangement is provided with a planetary gear train including: a centrally arranged sun gear wheel fixed to a drive shaft that extends in an axial direction of the wheel hub arrangement; a set of planet gear wheels distributed circumferentially around and meshing with the sun gear wheel; a ring gear wheel member extending circumferentially around the planet gear wheels and being provided with a ring gear wheel meshing with the planet gear wheels; a stationary planet wheel carrier; an annular rolling-element bearing arranged between the ring gear wheel member and the planet wheel carrier, wherein the ring gear wheel member is configured to be fixed to the driving wheel of the vehicle.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a 35 U.S.C. § 371 national stage application of PCT International Application No. PCT/EP2018/073967 filed on Sep. 6, 2018, the disclosure and content of which is incorporated by reference herein in its entirety.

TECHNICAL FIELD

The invention relates to a wheel hub arrangement for a driving wheel of a vehicle, wherein the wheel hub arrangement is provided with a planetary gear train.

The invention is particularly applicable in working machines within the fields of industrial construction machines or construction equipment, for instance wheel loaders. Although the invention will be described with respect to a wheel loader, the invention is not restricted to this particular machine, but may also be used in other working machines such as articulated haulers, excavators and backhoe loaders.

BACKGROUND

Hub-mounted reduction gears in the form of planetary gear trains are common for working machines, such as wheel loaders, articulated haulers, etc. Such gear trains include a centrally arranged sun gear wheel meshing with a set of planet gear wheels distributed circumferentially around the sun gear wheel and a ring gear wheel extending circumferentially around and meshing with the planet gear wheels. The sun gear wheel is driven by a drive shaft connected to a prime mover, such as an internal combustion engine or an electric motor, and a driving wheel of the working machine/vehicle is rotationally fixed to the ring gear wheel. A gear arrangement of this type also includes, for instance, a planet wheel carrier, that may be rotatable or stationary, and various roller bearings, such as between the ring gear wheel and a stationary component arranged radially inside of the ring gear wheel. US2014/0087913A1 discloses an example of a planetary transmission including a stationary planet wheel carrier.

Although hub-mounted planetary gear trains have been in use for a long time there is still a need for improvements with regard to weight, size and cost efficiency.

SUMMARY

An object of the invention is to provide a wheel hub arrangement that provides for improvements with regard to weight, size and cost efficiency. The object is achieved by an arrangement according to claim1. In another aspect of the invention the object is achieved by a vehicle provided with such an arrangement.

The invention relates to a wheel hub arrangement for a driving wheel of a vehicle, wherein the wheel hub arrangement is provided with a planetary gear train comprising: a centrally arranged sun gear wheel fixed to a drive shaft that extends in an axial direction of the wheel hub arrangement; a set of planet gear wheels distributed circumferentially around and meshing with the sun gear wheel; a ring gear wheel member extending circumferentially around the planet gear wheels and being provided with a ring gear wheel meshing with the planet gear wheels; a stationary planet wheel carrier; and an annular rolling-element bearing arranged between the ring gear wheel member and the planet wheel carrier, wherein the ring gear wheel member is configured to be fixed to the driving wheel of the vehicle.

The wheel hub arrangement is characterized in that the planet wheel carrier is provided with an annular depression that forms at least a part of an inner bearing race for the rolling elements of the rolling-element bearing.

The inner bearing race, or at least a part thereof, is thus provided directly in the planet wheel carrier, i.e. this part of the inner bearing race is integrated in the carrier component, instead of being provided in a separate inner bearing ring that normally is used to form the inner bearing race in a rolling-element bearing assembly. Such a design has the advantage of dispensing with the need for such a separate inner bearing ring, which in turn can be used to reduce the number, cost and weight of bearing components and it also enables a simplified process for assembling the arrangement. The annular depression may form the entire inner bearing case, in which case it would have a cross-section having the shape of a half circle if spherical rolling elements (balls) are to be used, or may form only a part of the inner bearing case, for instance half of the inner bearing race, in which case the cross-section would have the shape of a quarter of a circle for similar rolling elements.

That the planet wheel carrier is “stationary” means that the planet wheel carrier is rotationally fixed/immovable in relation to the arrangement as a whole so that each planet gear wheel is allowed to rotate only around its own axis but not around the sun gear wheel.

Each gear wheel in the gear train (sun wheel, planet wheels, ring wheel) is provided with some form of teeth configured to engage/mesh with corresponding teeth of another gear wheel. Planetary gear trains are well known as such.

That one component is “fixed to” another component, such as the sun gear wheel to the drive shaft, means that the components are fixed/attached/connected to each other so as to prevent relative (rotational) motion. Such components are thus connected in a rotationally locked manner so that if one component rotates also the other rotates in the same direction (in contrast to meshing gear wheels).

In an embodiment the ring gear wheel member is provided with a corresponding depression that forms at least a part of an outer bearing race for the rolling elements of the rolling-element bearing. This way, also the need for a separate outer bearing ring can be dispensed with, which leads to a further reduction in number, cost and weight of components.

In an embodiment the wheel hub arrangement comprises an annular extension member that is axially displaced in relation to the planet wheel carrier and fixed thereto along a first circumferentially extending mating surface, wherein an edge of the mating surface extends along the inner bearing race and wherein the annular extension member is provided with a further depression that forms a remaining part of the inner bearing race so that the inner bearing race is split between the planet wheel carrier and the annular extension member. This way the two parts (i.e. the planet wheel carrier and the annular extension member) can be hold separated axially during assembly of the wheel hub arrangement so as to allow the rolling elements to be properly positioned in the bearing before bringing the two parts together and forming the inner bearing race. Preferably, the edge of the first mating surface extends in the middle of the inner bearing race. Each of the two axially displaced parts will thus provide half of the inner bearing race.

As an alternative to splitting the inner bearing race, the outer bearing race may be split instead, i.e. an annular extension member may instead be fixed to the ring gear wheel member along the outer bearing race/the corresponding depression. However, splitting of the ring gear wheel member (the outer bearing race) is likely to require more space radially than splitting of the planet wheel carrier (the inner bearing race). In principal, splitting of both inner and outer components/bearing races is possible.

In an embodiment the ring gear wheel member comprises a ring wheel part and a bearing part that are axially displaced and fixed to each other along a second circumferentially extending mating surface, wherein the ring gear wheel is arranged on the ring wheel part and wherein the depression forming the outer bearing race is arranged in the bearing part. This provides for the possibility to use different material in the wheel part and the bearing part of the ring gear wheel member and thus to adapt the material to the particular function of the gear wheel and bearing parts. In turn this provides for the possibility to improve the function of the individual parts (e.g. a first material may be more suitable for forming teeth in the ring gear wheel and another material may be more suitable for forming a bearing race) and/or to reduce costs or weight (e.g. a first heavier and more costly material may be preferred for one part but a second lighter and cheaper material may be sufficient for the other part).

In an embodiment the planet wheel carrier is provided with a set of axially protruding supports for holding the planet gear wheels.

In an embodiment the planet wheel carrier is provided with a substantially flat annular surface facing in an axial direction away from the planet gear wheels. Preferably, a backside of each of the axially protruding supports for holding the planet gear wheels forms part of this substantially flat annular surface.

In an embodiment the arrangement is provided with a brake device comprising a set of brake disks and a brake piston arranged to press the brake disks together towards a brake support surface, wherein the flat annular surface of the planet gear wheel carrier forms the brake support surface. The planet wheel carrier thus provides three functions, it carries/provides support for the planet gear wheels, it provides at least a part of the inner bearing race for the rolling elements of the rolling-element bearing, and it provides the brake support surface. This can all be provided in one integral part, which reduces the total number of components.

According to another aspect of the invention the object is achieved by a vehicle comprising at least one driving wheel, wherein the driving wheel is provided with a wheel hub arrangement of the above type.

In an embodiment the vehicle is a working machine, such as a wheel loader or an articulated hauler.

Figure shows a side view of a vehicle1in the form of a wheel loader having a driving wheel2provided with a wheel hub arrangement according to the invention. The vehicle1is provided with at least one prime mover (not shown) arranged to drive the driving wheel2via the wheel hub arrangement. The prime mover may be an internal combustion engine or an electric motor.

FIGS. 2-7show different views of an embodiment of a wheel hub arrangement10according to the invention.

As shown inFIGS. 2-7the wheel hub arrangement10is provided with a planetary gear train comprising: a centrally arranged sun gear wheel11rotationally fixed to a drive shaft12that extends in an axial direction of the wheel hub arrangement10. The sun gear wheel11and the drive shaft12are not shown inFIGS. 2-3, and in the other figures the sun gear wheel11and the drive shaft12are only schematically illustrated. The drive shaft12is operatively connected to a prime mover of a vehicle, such as the vehicle1shown inFIG. 1.

A set of planet gear wheels13, in this case four, is distributed circumferentially around and meshing with the sun gear wheel11(seeFIG. 4). A ring gear wheel member, which in this case is made up of a ring wheel part14and a bearing part15, extends circumferentially around the four planet gear wheels13. The ring wheel part14is provided with a ring gear wheel16meshing with the planet gear wheels13.

A stationary (i.e. rotationally fixed/immovable) planet wheel carrier17is arranged to hold the planet gear wheels13by means of a corresponding set of axially protruding supports22. A planet gear wheel bearing130is arranged at each support22(seeFIG. 4). The planet wheel carrier17is fixed to an annular extension member18that is axially displaced in relation to the planet wheel carrier17. The planet wheel carrier17and the annular extension member18are fixed to each other along a first circumferentially extending mating surface20(see e.g.FIG. 7).

Each gear wheel in the gear train (sun wheel11, planet wheels13, ring wheel16) is in this case provided with regular gear teeth configured to engage/mesh with corresponding teeth of another gear wheel. In the case of the ring gear wheel16the teeth are directed radially inwards.

The ring gear wheel member, or rather the ring wheel part14thereof, is configured to be fixed to the driving wheel2of the vehicle1. Thereby, a rotational movement can be transmitted from the drive shaft12to the driving wheel2via the sun gear wheel11, the planet gear wheels13and the ring gear wheel16. The driving wheel2is arranged on the left (outer) side of the arrangement10with reference to the figures and may be connected directly to the ring wheel part14or via an intermediate part (not shown). Typically, the arrangement10comprises a cover (not shown) arranged at the ring wheel part14to cover and protect the gear wheels etc.

The wheel hub arrangement10further comprises an annular rolling-element bearing19arranged between the bearing part15of the ring gear wheel member and the planet wheel carrier17. In this case the bearing is arranged in a space delimited by three components: the bearing part15, the planet wheel carrier17and the annular extension member18. The bearing19comprises rolling-elements in the form of balls190and hollow cylinders191placed between the balls190(seeFIG. 5).

The planet wheel carrier17is provided with an annular depression17athat forms half of an inner bearing race for the rolling elements190of the rolling-element bearing19. An edge20aof the mating surface20between the planet wheel carrier17and the annular extension member18extends along the middle of the inner bearing race. The annular extension member18is provided with a further depression18athat forms a remaining half of the inner bearing race. Accordingly, the inner bearing race17a,18ais split evenly between the planet wheel carrier17and the annular extension member18(seeFIG. 7).

The bearing part15of the ring gear wheel member is provided with a corresponding depression15athat forms an outer bearing race for the rolling elements190of the rolling-element bearing19(seeFIG. 4and indication inFIG. 7).

Both bearing races15a,17a,18athus form in this example integrated parts of other components (bearing part15, planet wheel carrier17and annular extension member18).

When assembling the wheel hub arrangement10the balls190are positioned in the bearing19one at a time before bringing the planet wheel carrier17and the annular extension member18completely together axially.

The ring wheel part14and the bearing part15of the ring gear wheel member are connected to each other by means of fastening elements/bolts and corresponding holes140,150(seeFIG. 4). The ring wheel part14and the bearing part15are axially displaced and fixed to each other along a second circumferentially extending mating surface21(seeFIG. 4). Since the ring gear wheel16is arranged on the ring wheel part14and the depression forming the outer bearing race15ais arranged in the bearing part15, the two parts14,15can be made in different material adapted to the different purposes. For instance the ring wheel part14can be made of gear steel, such as case hardening steel, and the bearing part15can be made of bearing steel, such as induction hardening steel.

The mating surfaces20,21may comprise several mating sub-surfaces.

The planet wheel carrier17and the annular extension member18are connected to each other by means of fastening elements/bolts171and corresponding holes in the planet wheel carrier17and the annular extension member18(seeFIGS. 3, 4 and 7).

The wheel hub arrangement10is connectable to a support in the vehicle1by means of holes181distributed circumferentially around an outer rim of the annular extension member18(seeFIGS. 3, 4 and 7). This holds the arrangement10in place and makes the planet wheel carrier17“stationary”.

Further, the planet wheel carrier17is provided with a substantially flat annular surface23facing in an axial direction away from the planet gear wheels13, see e.g.FIG. 7. The wheel hub arrangement10is further provided with a brake device comprising a set of brake disks24and a brake piston (not shown) arranged to press the brake disks24together towards a brake support surface, wherein the flat annular surface23of the planet wheel carrier17forms the brake support surface.

The set of brake disks24comprises stator disks25, which are made of steel and are fixed to either of the stationary planet wheel holder17or the likewise stationary annular extension member18(by means of cut-outs at the perimeter of the stator disks25and pins arranged in the stationary components), and rotor disks26, which are provided with a friction coating/lining and are fixed to the sun gear wheel11or the drive shaft12(by means of splines). The principle structure of such a set of brake disks24is well known and all details are therefore not shown here. For instance, the sun gear wheel11and the drive shaft12are only schematically illustrated in the figures (as mentioned above) so the connection of the rotor disks26to the sun gear wheel/drive shaft11,12is not shown. Different variants of this connection are possible.

The principle function of the brake device, i.e. the set of brake disks24and the brake piston (not shown), is the following: the brake piston is moved axially towards the brake disks24(towards the left inFIG. 4) and presses the stator and rotor disks25,26together using the flat annular surface23on the “backside” of the planet wheel carrier17as support. This reduces or prevents rotation of the sun gear wheel/drive shaft11,12and thus reduces or prevents rotation of any driving wheel2fixed to the ring gear wheel member14,15. This principle function is also well known as such. The main thing in this disclosure is that the planet wheel carrier17, or rather its flat annular surface23on its “backside”, is used as brake support surface.

As an example, instead of splitting the inner bearing surface17a,18abetween two axially displaced components, a corresponding splitting can be arranged in the outer bearing surface15a. Further, the number of planet gear wheels13does not necessarily have to be four, the set of brake disks24may arranged differently that described above, etc.