Integrated differential and planetary support cover for AXLE assembly

Abstract

An axle assembly includes a main axle housing and an axle cover that combine to define an internal cavity in which a differential assembly and planetary gear assembly are disposed. The axle cover includes a plurality of walls that define saddle features, which receive bearings that support rotation of the differential assembly and the planet gear assembly. Bearing caps attach to the walls and secure the captured portions of the differential assembly and planet gear assembly to define an assembled unit. The assembled unit is attached to the main axle housing to enclose the cavity. An annulus gear is retained at the axle cover with the planetary gear assembly, and is received in the main axle housing and rotationally fixed by the main axle housing. A drive gear from the power source meshes with the planetary gear assembly or the differential assembly.

Description

INTEGRATED DIFFERENTIAL AND PLANETARYSUPPORT COVER FOR AXLE ASSEMBLYCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application is a PCT International Application, which claims priority to U.S. Provisional Application No. 63 / 619,364, filed January 10, 2024, the entire content of which is hereby incorporated by reference in its entirety.FIELD

[0002] The present disclosure relates to an axle for motor vehicles. More particularly, the present disclosure relates to a structural cover arrangement that includes integral features to support differential assembly bearings and planetary gearset support bearings.BACKGROUND

[0003] This section provides background information related to the present disclosure which is not necessarily prior art.

[0004] In view of the recent commitment of many vehicle OEM’s to develop electrified versions of various vehicles including vehicles having increased performance, higher vehicle mass, and increased payload capacity, updates to electrically driven axles are being developed. These electrically driven axle assemblies may include arrangements where the differential (which distributes power to a left and right ground engaging wheel) and a planetary gear are arranged coaxially about the axle’s output shaft. Such arrangements may also be utilized in vehicles with power sources other than electric motors, but typically advances in this area for revised axle designare electrically driven. These axle arrangements may include the outputs of the differential assembly each driving a separate planetary gearset or include a planetary gearset driving the differential assembly. Both of these arrangements provide the benefit of increased torque multiplication from the electric motor immediately prior to providing power to the ground engaging wheels. Such an arrangement may further reduce the load carrying requirements of the geartrain components prior to the differential and planetary gearset, providing cost and packaging benefits.

[0005] As electrically driven axles are now being utilized in vehicles of higher mass and payload capability, chassis loads are being transferred into the axle housing that surrounds and supports the geartrain of the electrically driven axles. It is preferred to provide an axle housing where a one-piece primary system housing provides a structural arrangement to counteract these chassis loads that are applied to the axle housing. Locating and supporting a differential and planetary gearset on the output axis, via such a one-piece primary system housing, increases the complexity of the housing design and the complexity of machining of the required supportive surfaces. This increased complexity is due to the need to have multiple locations disposed axially across the axle housing, which locations need to include features to support the bearings of the differential assembly, the planetary assembly, and the planetary ring gear. An example of a modified axle housing is shown in US11655890B2, where a separate planetary ring gear support is provided and fastened to an axle housing to provide a simplified axle housing design. Although such a design does provide for a simplified axle housing design, additional machining is still needed to adapt the planetary support to the axle housing. Additionally, with the planetary support being fastened to the axle housing on one face and extending away from the axle housing in a cantilevered manner, the arrangement results in a decreased stiffness than if the planetary supportwere integral to a surrounding housing or cover. Such an arrangement is also limited to only providing support to the planetary ring gear, with no support provided to bearings of the planetary gearset or differential.

[0006] Accordingly, there is a need to provide an alternative arrangement to support a planetary gearset, differential assembly, and planetary ring gear while maintaining a simplified axle housing design, preferably constructed of one main structural component.SUMMARY

[0007] This section provides a general summary of the many aspects associated with the inventive concepts embodied in the teachings of the present disclosure and is not intended to be considered a complete listing of its full scope of protection nor all of its features and advantages.

[0008] The present disclosure provides an integrated cover structure with improved stiffness to support the required components, further simplify the axle housing design, casting and subsequent machining, while providing a straightforward assembly process of the differential and planetary assemblies into the axle assembly.

[0009] The present disclosure is directed to an axle for motor vehicles where a main axle housing is provided with a structural cover which provides support for coaxially aligned differential bearing and planetary gearset components located on the axle’s output shaft axis. More particularly, the present disclosure provides two embodiments of a structural cover arrangement which include integral features to support differential assembly bearings and planetary gearset support bearings. Bearing caps partially surrounding these bearings are fastened to the cover. The planetary ring gear of the planetary gearset is captured between the cover and the main axle housing to provide location and support, coaxial with the differential assembly. Such anarrangement provides an improved assembly, an improved supportive structure, and a simplified main axle housing.

[0010] It is an aspect of the present disclosure to provide an axle assembly where a differential and at least one planetary assembly are located coaxially on the output axis, and an axle housing is provided that at least partially surrounds a motor, a geartrain, a differential, and a planetary assembly, and where a cover provides support for a differential and planetary gearset bearings.

[0011] It is a related aspect of the present disclosure to provide an axle arrangement where a joining plane of the axle housing and the cover is parallel and offset relative to the output axis, and the cover fastens against the axle to provide a sealed cavity.

[0012] It is a related aspect of the present disclosure to provide a cover including an integrated bearing saddle to receive and support bearings, which are further secured to the cover with bearing caps.

[0013] It is an aspect of the present disclosure to provide a cover including an integrated gear saddle to receive, support, and capture a first portion of the planetary ring gear, while the axle housing includes a second saddle feature to receive, support and capture a second portion of the planetary ring gear.

[0014] It is a related aspect of the present disclosure to provide a planetary ring gear with a flat portion on the outer diameter, which is received into a flat portion of the gear saddle of the axle housing to provide an anti-rotation feature for the planetary ring gear

[0015] It is an aspect of the present disclosure to provide a first cover assembly variant which includes a differential assembly, a first planetary assembly, a second planetary assembly,bearing supports for the differential and each planetary assembly, and further includes features to capture and support a first and a second planetary ring gear between the cover and the axle housing.

[0016] It is an aspect of the present disclosure to provide a second cover assembly variant which includes a first planetary assembly, a differential assembly, bearing supports for the differential and first planetary assembly, and further includes features to capture a planetary ring gear between the cover and the axle housing.

[0017] According to one aspect of the disclosure, an axle assembly includes: a main axle housing having an opening; an axle cover attached to the main axle housing over the opening, wherein the main axle housing and the axle cover define an internal cavity; a power source having an output; a differential assembly configured to transfer power toward ground engaging wheels; at least one planetary gear assembly operably coupled to the differential assembly; first and second axle outputs configured to drive the ground engaging wheels, wherein the first and second axle outputs are disposed downstream from the at least one planetary gear assembly and the differential assembly in the direction of power transfer from the power source to drive the ground the engaging wheels; wherein the at least one planetary gear assembly and the differential are coaxial with the first and second axle outputs; wherein a differential housing of the differential assembly is rotatable relative to the axle cover; wherein a carrier of the at least one planetary gear assembly is rotatable relative to the axle cover; wherein an annulus gear of the at least one planetary gear assembly surrounds the carrier and is partially received in the axle cover; wherein the at least one planetary gear assembly and the differential assembly are coupled with the axle cover and retained by the axle cover when the axle cover is separate and de-coupled from the main axle housing; wherein the differential assembly and at least one planetary gear assembly are positioned and supported for rotation within said internal cavity by the axle cover, and the annulus gear is capturedand rotationally fixed between the main axle housing and axle cover when the axle cover is mounted to the main axle housing

[0018] In one aspect, the axle cover includes a plurality of walls extending from the axle cover and formed as one-piece with the axle cover, wherein the walls each define a saddle feature, wherein the at least one planetary gear assembly and the differential housing are mounted on a respective saddle feature and axially located by said respective saddle feature.

[0019] In one aspect, wherein a plurality of bearings are secured to each of the saddle features between the differential housing and the respective saddle feature and between the at least one planetary gear assembly and the respective saddle feature.

[0020] In one aspect, a plurality of bearing caps are fastened to each of the walls and combine with the respective walls to circumferentially surround a portion the differential housing and the response bearing and to circumferentially surround a portion of the carrier of the at least one planetary gear assembly and the respective bearing.

[0021] In one aspect, the bearing caps and walls combine to secure the at least one planetary gear assembly and the differential assembly to the axle housing when the axle housing is separate from the main axle housing.

[0022] In one aspect, the axle cover defines a cover annulus saddle portion, wherein a first portion of the annulus gear is received in the cover annulus saddle portion, and a second portion of the annulus gear is exposed out from axle cover when the axle cover is separate from the main axle housing.

[0023] In one aspect, the annulus gear is fixed against rotation relative to the annulus saddle portion when the axle cover is mounted to the main axle housing.

[0024] In one aspect, the main axle housing defines a housing annulus saddle portion, wherein the second portion of the annulus gear is received in the housing saddle portion when the axle cover is mounted to the main axle housing.

[0025] In one aspect, the annulus gear includes a flat outer surface and the main housing includes a flat inner surface on the housing annulus saddle portion, wherein the flat outer surface abuts against the flat inner surface and fixes the annulus gear against rotation when the axle cover is mounted to the main axle housing.

[0026] In one aspect, the bearing caps and walls each define half circles and define a full circle when mated together.

[0027] In one aspect, the walls are proud relative to a mounting flange of the cover, wherein the mounting flange corresponds to a housing flange of the main axle housing that surrounds and defines the opening of the main axle housing, such that the walls extend through the opening defined by the main axle housing when the axle cover is mounted to the main axle housing.

[0028] In one aspect, the power source is a motor, and the motor drives a drive gear, which is in meshed engagement with the driven gear that is fixed to the differential housing, wherein the motor and the drive gear are at least partially disposed within main axle housing.

[0029] In one aspect, the first and second axle outputs are fixed to first and second axle shafts, respectively, wherein the first and second axle shafts drive the ground engaging wheels.

[0030] In one aspect, the at least one planetary gear assembly includes a first planetary gear assembly and a second planetary gear assembly disposed on opposite axial sides of the differential assembly, wherein the first and second planetary gear assemblies respectively include first and second sun gears, first and second carriers, first and second pluralities of planet gearsattached to the first and second carriers and meshed with the first and second sun gears, and first and second annulus gears meshed with the planet gears, wherein the planet gears roll along the annulus gears and rotate the carrier in response to rotation of the sun gear; wherein a first bevel gear of the differential is fixed to the first sun gear; wherein a second bevel gear of the differential is fixed to the second sun gear; wherein the first carrier is fixed to the first axle output; wherein the second carrier is fixed to the second axle output; wherein the power source drives a gear set including a driven gear fixed to the differential housing, wherein rotation of the differential housing transmits power via the differential housing to the bevel gears, wherein rotation of the bevel gears transmits power to the sun gears, wherein rotation of the sun gears transmits power to the first and second axle outputs via the first and second planetary gear assemblies.

[0031] In one aspect, the first carrier is attached to a bearing held in a saddle of a first carrier wall and captured by a corresponding bearing cap; wherein the second carrier is attached to a bearing held in a saddle of a second carrier wall and captured by a corresponding bearing cap; wherein the first bevel gear is attached to a first differential bearing held in a saddle of a first differential wall and captured by a corresponding bearing cap; wherein the second bevel gear is attached to a second differential bearing held in a saddle of a second differential wall and captured by a corresponding bearing cap; wherein the first annulus gear is disposed axially between the first carrier wall and the first differential wall, wherein a portion of the first annulus gear is held in a saddle formed in the axle housing; wherein the second annulus gear is disposed axially between the second carrier wall and the second differentia wall, wherein a portion of the second annulus gear is held in a saddle formed in the axle housing; wherein the first and second carrier walls are outboard relative to the first and second differential walls; wherein the carrier walls and thedifferential walls are formed as one-piece with the axle cover, wherein the bearing caps are separate and fixedly fastened to the walls.

[0032] In one aspect, the at least one planetary gear assembly is a first planetary gear assembly disposed on a first axial side of the differential assembly, wherein the first planetary gear assembly includes a first sun gear, a first carrier, a first plurality of planet gears attached to the first carrier and meshed with the first sun gear, and a first annulus gear meshed with the planet gears, wherein the planet gears roll along the annulus gear and rotate the carrier in response to rotation of the sun gear; wherein the first carrier is fixed to the differential housing; wherein a first bevel gear of the differential is fixed to the first axle output; wherein a second bevel gear of the differential is fixed to the second axle output; wherein the power source drives a gear set including a driven gear fixed to the first sun gear, wherein rotation of the first sun gear transmits power to the carrier via the planetary gear assembly, wherein rotation of the carrier transmits power to the differential housing, wherein rotation of the differential housing transmits power to the bevel gears, wherein rotation of the bevel gears transmits power to the first and second axle outputs.

[0033] In one aspect, the differential housing is attached to a differential housing bearing held in a saddle of a differential housing wall and captured by a corresponding bearing cap; wherein a shaft of the sun gear is attached to a shaft bearing held in a saddle of a sun gear shaft wall and captured by a corresponding bearing cap; wherein the second bevel gear is attached to a differential bearing held in a saddle of a differential wall and captured by a corresponding bearing cap; wherein the first annulus gear is disposed axially between the sun gear shaft wall and the differential housing wall, wherein a portion of the first annulus gear is held in a saddle formed in the axle housing; wherein the sun gear shaft wall and differential wall are outboard relative to thedifferential housing wall; wherein the walls are formed as one-piece with the axle cover, wherein the bearing caps are separate and fixedly fastened to the walls.

[0034] In another aspect of the disclosure, a method of assembling an axle assembly includes: providing an axle cover having a plurality of walls formed as one-piece with the axle housing, wherein each of the walls extend from the axle cover and define corresponding saddle features; attaching a differential assembly to the axle cover, wherein the differential assembly includes a differential housing rotatably supported in the axle cover and side gears for driving ground engaging wheels; attaching at least one planetary gear assembly to the axle cover, wherein the at least one planetary gear assembly is operatively coupled to the differential gear assembly to transfer torque therebetween; wherein the at least one planetary gear assembly includes an annulus gear meshed with and surrounding a plurality of planet gears attached to a planet carrier, and a sun gear meshed with the planet gears; wherein the at least one planetary gear assembly is coaxial with the differential gear assembly; wherein the differential housing and the at least one planetary gear assembly are attached to bearings received in corresponding saddle features formed in wall portions of the axle cover; attaching bearing caps to the wall portions, wherein the bearing caps combine with the walls to fully surround the bearings and retain the differential assembly and the at least one planetary gear assembly to the axle cover, wherein the differential assembly, the at least one planetary gear assembly, and axle cover define an assembled unit; attaching the assembled unit to the main axle housing and receiving the differential assembly and the at least one planetary gear assembly in an interior cavity defined by the main axle housing and the axle cover.

[0035] In one aspect, the annulus gear, as part of the assembled unit, is exposed, wherein the annulus gear is received in a corresponding saddle formed in the main axle housing; whereinthe main axle housing includes an inner flat surface that abuts an outer flat surface of the annulus gear and fixes the annulus gear against rotation relative to the main axle housing and the axle cover.

[0036] In one aspect, a drive gear of a power source is disposed within the main axle housing, and the drive drivingly engages a driven gear to provide torque to the at least one planetary gear assembly and the differential assembly, wherein the driven gear is fixed to a sun gear of the at least planetary gear assembly or to the differential housing of the differential assembly.

[0037] These and other features and advantages of the present disclosure will be more readily appreciated when considered in connection with the following detailed description and appending drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The drawings described herein are for illustrative purposes only of selected embodiments and are not intended to limit the scope of the present disclosure. The inventive concepts associated with the present disclosure is / are more readily understood by reference to the following description in combination with the accompanying drawings wherein:

[0039] FIG. 1 is an arrangement of a first embodiment of the axle assembly with a differential driving dual output planetary gears utilizing the supporting cover assembly;

[0040] FIG. 2 is an isometric view of the cover assembly of the first embodiment;

[0041] FIG. 3 is an isometric view of the cover of the first embodiment;

[0042] FIG. 4 is a sectional view of the planetary ring gear support between the cover and the axle housing;

[0043] FIG. 5 is sectional view of a bearing support by the cover assembly; and

[0044] FIG. 6 is an arrangement of a second embodiment of the axle assembly with a planetary driving a differential utilizing the supporting cover assembly.DETAILED DESCRIPTION

[0045] The present disclosure provides an axle for motor vehicles having a main axle housing, and a separate cover is attached to the main axle housing and provides support for the differential bearing and planetary gearset components located on the output axis. Two embodiments of a structural cover arrangement are provided. Both embodiments include a cover, which supports a differential gearset via a pair of support bearings and further supports a planetary gearset. The planetary gearset is supported via a support bearing at a first location, while the planetary ring gear is supported by being captured between the cover and the axle housing. Bearing caps attached to the cover are utilized to support and locate the bearings. The cover assembly is fastened to the axle housing and provides a sealed cavity.

[0046] The first embodiment includes an axle arrangement where an electric motor drives a gearset, which is coupled to a driven gear on the differential assembly. The differential is utilized to indirectly distribute torque to a left and right ground engaging wheel. Each output of the differential drives a respective planetary gearset positioned adjacent and coaxial with the differential, where the sun gear is driven by the output of the differential, a ring gear is held stationary, and each planetary carrier drives the ground engaging wheel via an axle shaft. The cover assembly will provide support for a pair of differential bearings, a bearing to support and position each planetary carrier, and features to capture and support the ring gear between the cover and the axle housing.

[0047] The second embodiment includes an axle arrangement where an electric motor drives a gearset which is coupled to a sun gear of a planetary gearset. The carrier of the planetary gearset drives the differential assembly, while the planetary ring gear is held stationary. The differential is utilized to distribute torque to a left and right ground engaging wheel via a pair of axle shafts. The planetary gearset is positioned adjacent and coaxially with the differential. The cover assembly provides support for a pair of differential bearings, a bearing to support and position the sun gear of the planetary gearset, and additional features to capture and support the ring gear between the cover and the axle housing.

[0048] Each arrangement provides for an improved axle assembly, an improved support structure due to a one-piece primary axle housing, and a simplified main axle housing. With such an arrangement the main housing no longer needs to incorporate the various complex features to support the bearings of the differential and planetary assembly, resulting in a simpler design which is easier to cast and machine. Machining of the bearing bores and caps are required only on the cover portion, which is easier due to the reduced size of the cover when compared to the main axle housing. Further any adjustments to bearing preload or gearset positioning can be performed more easily on the cover assembly than on a complete axle housing.

[0049] With initial attention directed to FIG. 1 , an arrangement of a first embodiment of the axle assembly 20 is shown, with a differential assembly 48 driving dual output planetary gear assemblies 68A, 68B, with the axle assembly 20 utilizing the supporting cover assembly 24. The orientation of this axle assembly 20 is shown as a rear axle in a vehicle and viewed from above (Z axis) as positioned in the vehicle. However, it will be appreciated that such an arrangement may be used at other axle locations. Axle assembly 20 includes a main axle housing 22 and cover assembly 24. Axle shafts 26A and 26B are provided to output power of the axle assembly 20 toground engaging wheels 28A and 28B. Axle shafts 26 are located at a Y axis position of zero and rotate about the X axis as shown in FIG. 1. Axle assembly 20 may further include tubes 30 fixed to axle housing 22 or integral with axle housing 22 to create a beam axle arrangement, where chassis loads are applied to tubes 30 via shock mounts or springs not shown. Axle shafts 26 pass through and may be further supported by tubes 30 via bearings near the wheel ends, although not specifically shown in FIG. 1. Axle housing 22 may be designed as a primarily one-piece housing with a rear opening 32 (thereby providing access from the rear when the cover assembly 24 is removed). Utilizing a one-piece housing provides an improved structure able to receive chassis loads directly via axle housing 22 or via tubes 30. An integral axle housing flange 34 is provided around the circumference of rear opening 34 on the X-Z plane, and may be offset rearward from center of axis X. Cover assembly 24 includes a similar shaped flange 36 integrated into cover 38. A plurality of fasteners 40 are provided around the flanges 34 and 36 to attach cover assembly 24 to axle housing 22, resulting in the sealing off of rear opening 32, thereby providing a robust connection and structure between cover assembly 24 and axle housing 22, and creating internal cavity 39.

[0050] Continuing to refer to FIG. 1, a motor 40 and gearset 42 may be provided at least partially within cavity 39. Axle housing 22 may provide features to locate and support motor 40 and gearset 42. In a non-limiting example of gearset 42, the output of motor 40 is coupled for rotation with drive gear 44. Drive gear 44 is in a constant meshed engagement with driven gear 46. Driven gear 46 is fixed for rotation with differential assembly 48, and more specifically to differential housing 50. Gearset 42 is provided as a simple two gear arrangement, but other gearsets with additional gear stages, gearsets, and / or gear types may be utilized as desired to achieve appropriate reduction ratios or arrangements. Differential gear assembly 48 is illustrated as astandard bevel differential known by those in the art. However, various differential arrangements may be used. Differential gear assembly 48 is supported by a pair of bearings 52A and 52B to rotate about the X axis. Differential support bearings 52 may utilize taper or ball bearing elements between an inner and outer race element as known in the art. Differential support bearings 52A and 52B may be supported by features integral to cover 38. In one aspect, a pair of forward extending supporting walls 54A and 54B are each integrated into cover 38 as a one-piece component and extend toward the centerline of differential gear assembly 48 and the X axis. The supporting features of differential bearing 52A is described herein in more specific detail, and it will be understood the supporting features of differential bearing 52B are the same, but on the right side of differential assembly 48 as seen in FIG. 1.

[0051] With reference to the supporting features of differential bearing 52A, wall 54A extends from cover 38 and includes a half circular shaped saddle 56A to receive and partially surround the outer race portion of differential bearing 52A. In particular, the rear half of differential bearing 52A on the side of cover 38 is received into the half-circular shaped saddle 56A of wall 54A. This arrangement results in approximately half of the front portion of differential bearing 52A being exposed after it is placed into saddle 56A along with differential assembly 48. A bearing cap 58A with a similar half-circular feature 60A will surround the outer race portion of bearing 52A that is not received into saddle 56A, once the feature 60A is installed onto cover 38, to be received into housing 22 when the cover 38 is mounted thereto. Bearing cap 58A is secured to wall 54A via a pair of fasteners 62, resulting in the outer race of bearing 52A being fully surrounded and supported by wall 54A and bearing cap 58A. Differential bearing 52B is supported by wall 54B, installed into saddle feature 56B, and further surrounded by bearing cap 58B in a similar manner as differential bearing 52A. This arrangement results in differential gear assembly 48 beingsupported and extending into cavity 39 with walls 54A and 54B integrated into cover 38. Support of differential gear assembly 48 is therefore solely provided by the cover 38, and the positioning of the differential gear assembly 48 relative to axle shafts 26 and gearset 42 is provided by the attachment of cover 38 to the axle housing flange 34.

[0052] During operation, differential gear assembly 48 will receive power from driven gear 46, resulting in power being transferred through differential housing 50, and into bevel gear arrangement 64. Bevel gear arrangement 64 includes a first side gear 66A coupled for rotation to first planetary gear assembly 68A and specifically to sun gear shaft 70A. A second side gear 66B is coupled for rotation to second planetary gear assembly 68B and specifically to sun gear shaft 70B. At least one pair of bevel pinion gears 72 are meshed with side gears 66A and 66B. Pinions 72 are rotatably supported on a pinion shaft (not shown) in differential housing 50. Power therefore is provided from motor 40 to differential gear assembly 48 via gearset 42. The fixed connection of driven gear 46 to differential assembly 48 will therefore transmit power to differential housing 50, into bevel differential gearset 64, which splits and distributes power to the first 68A and second 68B planetary gear assemblies.

[0053] Both planetary gear assemblies 68A and 68B are of the same design. The first planetary gear assembly 68A will be referenced in further detail below. First Planetary assembly 68A includes an annulus gear 74A, and a plurality of pinion gears 76A are positioned in constant meshed engagement with sun gear 78A and annulus gear 74A. Sun gear 78A is fixed for rotation to sun gear shaft 70A, which is driven by first side gear 66A. Carrier 80A includes pinion shafts 82A rotatably supporting the plurality of pinion gears 76A. Annulus gear 74A is fixed relative to axle housing 22 and cover 38. The output of planetary gear assembly 68A is carrier 80A which has a fixed connection at the inboard end of axle shaft 26A. The pinion gears 76A, which areequally spaced around the central axis of rotation, mesh with the sun gear 78A as well as annulus gear 74A, such that they orbit as they roll. All of the pinion gears 76 A are mounted to the single rotating carrier 80A via pinion shafts 82A. As the carrier 80A rotates, the carrier 80A delivers low- speed, high-torque output to axle shaft 26A fixed thereto. It will be understood that second planetary assembly 68B includes the same components, connections, and functionality as described for first planetary assembly 68A with reference character B being used for like components.

[0054] Continuing to refer to FIG. 1 and first planetary assembly 68A, for proper functionality, annulus gear 74A is be held against rotation, supported in a manner to counteract loading, and maintains its position relative to the rolling pinion gears 84A and rotating sun gear 78A. Carrier 80A is also supported and precisely positioned while allowing for rotation about axis X. Axle shaft 26A is supported on the inboard end, providing a concentric arrangement to planetary assembly 68A. As will be understood, the features to support annulus gear 74A and carrier 80A will also be applicable to annulus gear 74B and carrier 80B of second planetary assembly 68B. To continue to maintain a simplified axle housing 22, features are included on cover 38 to fully or partially provide support and location of annulus gear 74 A and carrier 80A. A bearing 86A is provided which directly or indirectly supports carrier 80A of first planetary 68A and axle shaft 26A. Bearing 86A may directly support an outboard portion of carrier 80A or may support an inboard end of axle shaft 26A near carrier 80A. Support bearing 86A may be a ball, roller, bushing, or taper bearing as required. As axle shaft 26A and carrier 80A are connected and fixed for rotation together, providing bearing 86A at either location will provide acceptable support for both components. Similar to the support provided to differential bearing 52A and 52B by cover 38, a supporting wall 88A is provided as a feature extending forward toward bearing 86A and the X axisand is integrally connected to cover 38. Supporting wall 88 A extends from cover 38 and includes a half-circular shaped saddle 90A to receive and partially surround the outer race portion of support bearing 86A. In particular, the rear half of support bearing 86 A is received into the half-circular shaped saddle 90A of wall 88A. This arrangement results in approximately the front half portion of support bearing 86A exposed when placed into saddle 90A. A bearing cap 92A with a similar half-circular saddle 94A is installed over the front half of bearing 86A, surrounding the outer race portion of bearing 86A that was not received in saddle 90A. Bearing cap 92A is secured to wall 88A via a pair of fasteners 96, resulting in bearing 86A being fully surrounded and supported by the combination of wall 88A and bearing cap 92A. A matching supporting wall 88B is provided to support bearing 86B on the opposite axial side, outboard of planetary assembly 68B. Support bearing 86B is supported by wall 88B, installed into saddle feature 90B, and further surrounded by bearing cap 92B in a similar manner as support bearing 86A. Carrier 80A and 80B are supported and extend into cavity 39 by respective walls 88A and 88B integrated into cover 38. Support of carrier 80A or 80B is therefore solely provided by cover 38. Positioning of planetary assembly 68A and 68B relative to axle shafts 26, and the differential assembly 48 about the axis X, is provided by the attachment of cover 38 to axle housing flange 34.

[0055] Referring now to both FIG. 1 and FIG. 2, annulus gears 74A and 74B are held in place to prevent rotation relative to axle housing 22, and are supported in a manner to counteract loading developed within the planetary gears of planetary assembly 68A and 68B, while maintaining the position and alignment relative to pinion gears 84A or 84B in an axial direction. With reference to annulus gear 74A, with the support features for annulus gear 74B being the same, a short supportive wall 100A extends from cover 38 and includes a circular shaped saddle 102 A to receive and partially surround the outer portion of annulus gear 74A. Most of saddle 102A isintegrated directly into cover 38 without an extensive extending wall portion 100A projecting from the cover 38, because the cover 38 is designed to closely follow the outer diameter 110 of annulus gear 74A. In particular, the rear portion 104 of annulus gear 74A is received into circular shaped saddle 102A of wall 100A and / or cover 38. The forward portion 106 of annulus gear 74A is received into saddle 108A, which is formed as part of axle housing 22. Annulus gear 74A is therefore captured between saddle 102A of cover 38 and saddle 108 A of axle housing 22, providing a fully surrounding support structure and ensuring the position of the annulus gear 74A is correct relative to the other components of planetary assembly 68A. An anti-rotation feature (flat 112) between the outer diameter 110 of annulus gear 74 and axle housing 22 is utilized to ensure annulus gear 74 is fixed for rotation relative to the axle housing 22 and cover 38. As best seen in FIG. 2 or 4, flat 112 is provided on the outer diameter 110, which is shown located on the top portion and bottom portion of annulus gear 74. A similar flat face 114 is provided in a portion of the saddle 108A of axle housing 22, resulting in annulus gear 74 being received into the saddle 108 in a specific orientation to align flats 112 and 114 together. Once annulus gear 74 is fully installed and cover 38 is attached to housing 22, annulus gear 74 is captured and is fixed against rotation.

[0056] Such an arrangement accordingly provides a cover assembly 24 that includes a cover 38 with integral features as previously described to support and attach differential assembly 48, first planetary assembly 68 A, and second planetary assembly 68B to cover 38. Annulus gears 74A and 74B are positioned, in a partially supported state by saddles 102A and 102B, surrounding planetary assemblies 68A and 68B. Such a cover assembly 24 is beneficial because these components can be assembled offline from the remaining portion of axle assembly 20, including setting of bearing preloads and gear lashes as required. In one aspect, the annulus gears 74A and74B, as part of the planetary assemblies, are installed into the cover 38, followed by the caps 58 A, 58B and 92A, 92B. Cover assembly 24, with the caps installed, may then be installed by inserting the assembly into rear opening 32 of axle housing 22, seating annulus gears 74A and 74B into saddles 108 of housing 22. Driven gear 46, held by cover assembly 24, will also mesh with drive gear 44. Once cover assembly 24 is fully seated against flange 34, a plurality of fasteners 40 are installed around cover flange 36 and received by threaded bores in housing flange 34. Axle shafts 26A and 26B may then be inserted axially to connect with carrier 80A and 80B, respectively.

[0057] Referring to FIG. 2, an isometric view of cover assembly 24 with cover 38, differential assembly 48, first planetary assembly 68A, second planetary assembly 68B, annulus gears 74A and 74B, and bearing caps 58 and 92 is shown. An improved view of cover flange 36 is also shown, with openings 116 to pass fasteners 40 through to connect to housing flange 34. Fasteners 40 are provided fully around cover flange 36 to secure cover assembly 24 to axle housing 22. As previously described, bearing caps 58A and 58B, surrounding differential support bearings 52A and 52B, are attached to wall 54 via a pair fasteners 62. In a similar manner, bearing caps 92A and 92B surround planetary carrier support bearing 86A and 86B, captured between saddles 90A, 90B and 94A, 94B. Bearing caps 92A, 92B are secured to wall 88A, 88B with a pair of fasteners 96. In this view, it is shown how annulus gear 74A, 74B, and in particular rear portion 104, is received into cover 38 by saddle 102A, 102B of wall 100A, 100B, partially leaving the forward portions 106 exposed. With the annulus gears 74A, 74B surrounding the corresponding carrier and pinions, the gears 74A and 74B are retained with the cover 38.

[0058] FIG. 3 provides a view of cover 38 without any components installed, in order to see the extending integrated walls and various features to receive components in better detail. As can be seen, cover 38 includes a cover flange 36 which fully surrounds the main portion of cover38 with a flat face, which will mate to housing flange 34 with a plurality of fasteners. Cover 38 may be a cast component, possibly made from aluminum or cast iron, so wall features 54, 88, and100 integral provide an improved structure. Further ribbing or material may be added beyond what is shown in the proposed design to further stiffen and provide structural rigidity to cover 38. In this view, walls 54 are shown with features to support the differential bearings 52 and differential assembly 48, and walls 88 are shown with features to support bearings 86 and planetary assemblies 68, which are similar in construction and extend away from flange 36. The walls include a saddle feature 56 or 90 to receive and surround approximately half of bearings 52 and 86. Saddles 56 or 90 may be concentrically located relative to each other and positioned about the X axis as previously described. Saddles 56 or 90 may be positioned within walls 54 and 88 in a manner where the entire arc of the saddle is positioned proud of cover flange 36. In contrast, the saddle feature 102, to receive the rear of annulus gear 74, may be a larger diameter and therefore result in a shorter extending wall 100 when compared to walls 54 and 88. Wall 100 may only extend from the body of the cover 38, where saddle 102 surrounds the upper or lower extent of annulus gear 74. Saddle feature 102 may intersect or extend in the negative Y direction beyond cover flange 36 due to the increased outer diameter 110 of annulus gear 74 which will further improve the rigidity of cover 38. Cover 38 may also incorporate a pocket 118 to surround driven gear 46 without contact between walls 54A and 54B. Shoulders 120 may be provided with cover 38 as features on the edges of saddles 56, 90, and / or 102 to assist in positioning and supporting axial movement and loads of bearings 52 and 86 and / or annulus gear 76 as necessary.

[0059] FIG. 4 is a sectional view taken through the YZ plane of annulus gear 74 to further show how annulus gear 74 is captured between cover 38 and axle housing 22 to prevent rotation and provide support. A short supportive wall 100, mostly in an upper and lower area, extendsfrom cover 38 and include a circular shaped saddle 102 to receive and partially surround the rear outer portion of annulus gear 74. As shown, the vertically central portion of saddle 102 is integrated directly into cover 38 without an extensive extending wall portion 100 projecting from the cover 38, because the cover 38 is designed to closely follow the outer diameter 110 of annulus gear 74. Approximately a third of the rear portion 104 of annulus gear 74 is received into circular shaped saddle 102 of wall 100 and / or cover 38. The remaining forward portion 106 of annulus gear 74 is received into saddle 108, which is formed as part of axle housing 22. The forward portion 106 of annulus gear 74 includes the anti-rotation feature in the form of flat 112, provided on the outer diameter 110 of annulus gear 74, and a mating flat 114 provided as a receiving feature of axle housing 22. These flats 112 and 114 are utilized to ensure annulus gear 74 is fixed for rotation relative to the axle housing 22 and cover 38. When cover assembly 26, including annulus gear 74, is installed with axle housing 22, annulus gear 74 is captured between saddle 102 of cover 38 and saddle 108 of axle housing 22, providing a fully surrounding support structure, and ensuring the position of the annulus gear 74 is correct relative to the remaining components of planetary assembly 68.

[0060] FIG. 5 provides a sectional view taken through wall 54, which supports differential bearing 52 in the plane YZ. Wall 54 extends from cover 38 and includes half-circular shaped saddle 56 to receive and partially surround the outer race portion of differential bearing 52. In particular, the rear half of differential bearing 52 toward cover 38 is received into the half circular shaped saddle 56 formed in wall 54. This results in approximately the front half portion, toward axle housing 22, of differential bearing 52 exposed after it is placed into saddle 56. Bearing cap 58 with a similar half circular saddle feature 60 surround the outer race portion of bearing 52 that is not received in saddle 56, once the cap 58 is installed to cover 38. Bearing cap 58 is secured towall 54 via a pair of fasteners 62, resulting in the outer race of bearing 52 being fully surrounded and supported by the combination of wall 54 and bearing cap 58. In this view, it is shown that bearing 52 surrounds a hollow portion of differential housing 50 to provide support. The sun gear shaft 82 attached to the side gear 66 is seen at the center of the section.

[0061] FIG. 6 provides a second embodiment of an axle assembly 220, where a planetary assembly drives a differential assembly, both located on the output axis, and utilizes an alternative supporting cover assembly. The orientation of this view of axle assembly 220 is again provided as a rear axle in a vehicle and viewed from above (Z axis) as positioned in the vehicle. Axle assembly 220 includes a main axle housing 222 and cover assembly 224. Axle shafts 226A and 226B are provided to transmit output power of axle assembly 220 to ground engaging wheels 228A and 228B. Axle shafts 226 are located at a Y axis equal to zero and rotate about the X axis as shown in FIG. 6. Axle assembly 220 may further include tubes 230 fixed to axle housing 222 or integral to axle housing 222 to create a beam axle arrangement, where chassis loads are applied to tubes 230 via shock mounts or springs not shown. Axle shafts 226 may pass through and be further supported by tubes 230 via bearings at or near the wheel ends, although not specifically shown in FIG. 6. Axle housing 222 may be designed as a primarily one-piece housing with a rear opening 232. Utilizing a one-piece housing provides an improved structure able to receive chassis loads directly via axle housing 222 or via tubes 230. An integral axle housing flange 234 is provided around the circumference of rear opening 234 on the X-Z plane and may be offset rearward from center of axis X. Cover assembly 224 includes a similar shaped flange 236 integrated into cover 238. A plurality of fasteners 240 are provided around the flanges 234 and 236 to attach cover assembly 224 to axle housing 222, resulting in a sealing off of rear opening 232, providing a robustconnection and structure between cover assembly 224 and axle housing 222, and creating internal cavity 239.

[0062] Continuing to refer to FIG. 6, a motor 240 and gearset 242 may be provided at least partially within cavity 239. Axle housing 222 may provide features to locate and support motor 240 and gearset 242. In a non-limiting example of gearset 242, the output of motor 240 is coupled for rotation to drive gear 244. Drive gear 244 is in a constant meshed engagement with driven gear 246. Gearset 242 is provided as a simple two gear arrangement, but other gearsets with additional gear stages, gearsets, and / or gear types may be utilized as desired to achieve appropriate reduction ratios or arrangements. Driven gear 246 is fixed for rotation to a sun gear shaft 270. Sun gear shaft 270 is a hollow shaft, surrounding and concentric with axle shaft 226B (shown on the right of differential 248 in FIG. 6; but it will be appreciated that the sun gear shaft 270 could also surround shaft 226A), and is supported on a first end 271 (outboard end) by bearing 286. Support bearing 286 may be a ball, roller, bushing, or taper bearing as required. Similar to the previous embodiment, a supporting wall 288 is integral with cover 238 and is provided as a feature extending toward bearing 286 and the X axis. Supporting wall 288 extends from cover 238 and includes a half-circular shaped saddle 290 feature to receive and partially surround the outer race portion of support bearing 286. In particular, the rear half of support bearing 286 is received into the half-circular shaped saddle 290 of wall 288. This results in the front half portion of support bearing 286 being exposed as it is placed into saddle 290. A bearing cap 292 with a similar halfcircular saddle 294 is installed, surrounding the outer race portion of bearing 286 that is not received in saddle 290 (the front half portion). Bearing cap 292 is secured to wall 288 via a pair of fasteners 296, resulting in bearing 286 being fully surrounded and supported by wall 288 and bearing cap 292. On the second end 273 (inboard end) of sun gear shaft 270, a sun gear 278 isprovided, either integrally as part of sun gear shaft 270 or as a separate sun gear fixed to sun gear shaft 270. Sun gear 278 provide the power input to planetary assembly 268 from driven gear 246.Planetary assembly 268 includes an annulus gear 274 and a plurality of pinion gears 276 positioned in constant meshed engagement with the sun gear 278 and the annulus gear 274. Carrier 280 includes pinion shafts 282 rotatably supporting the plurality of pinion gears 276. Annulus gear 274 is fixed relative to axle housing 222 and cover 238. The output of planetary gear assembly 268 is carrier 280, which has a fixed connection to differential assembly 248 and specifically to differential housing 250. Differential assembly 248 and planetary gear assembly 268 are coaxially arranged about axis X and the output axle shafts 226. The pinion gears 276, equally spaced around the central axis of rotation, mesh with the sun gear 278 as well as annulus gear 274, such that they orbit as they roll. All of the pinion gears 276 are mounted to a single rotating carrier 280. As the carrier 280 rotates, it delivers low-speed, high-torque output to differential housing 250.

[0063] Differential gear assembly 248 is shown as a standard bevel differential known by those in the art. Differential gear assembly 248 is supported by a pair of bearings 252A and 252B to rotate about the X axis. Differential support bearings 252 may utilize taper or ball bearing elements between an inner and outer race element as known in the art. Differential support bearings 252A and 252B are supported by features integral to cover 238. A pair of extending supporting walls 254A and 254B are each integrated into cover 238 as a one-piece component, and extend toward the centerline of differential gear assembly 248 and the X axis. The supporting features of differential bearing 252A are described in further detail, but it will be understood that the supporting feature of differential bearing 252B are the same, but on the right side of differential assembly 248 as seen in FIG. 6. Wall 254A extends from cover 238 and includes a half-circular shaped saddle 256A to receive and partially surround the outer race portion of differential bearing252A. In particular, the rear half of differential bearing 252A towards cover 238 is received into the half-circular shaped saddle 256A of wall 254A. This results in approximately the front half portion of differential bearing 252A exposed after it and differential assembly 248 are placed into saddle 256A. A bearing cap 258A with a similar half-circular feature 260A surround the outer race portion of bearing 252A that is not received in saddle 256A once the cap 258A is installed onto cover 238. Bearing cap 258A is secured to wall 254A via a pair of fasteners 262, resulting in the outer race of bearing 252A being fully surrounded and supported by wall 254A and bearing cap 258A. Differential bearing 252B is supported by wall 254B, installed into saddle feature 256B, and further surrounded by bearing cap 258B in a similar manner as differential bearing 252 A. This results in the differential gear assembly 248 being supported and extending into cavity 239 by the walls 254A and 254B integrated into cover 238. Support of differential gear assembly 248 is solely provided by cover 238, although positioning of the differential gear assembly 248 relative to axle shafts 226 and gearset 242 is provided by the attachment of cover 238 to axle housing flange 234.

[0064] Differential gear assembly 248 receives power from a fixed connection between differential housing 250 and planetary carrier 280. Power is transmitted through differential housing 250 and into bevel gear arrangement 264. Bevel gear arrangement 264 further includes a first side gear 266A coupled for rotation to first axle shaft 226A. A second side gear 266B is coupled for rotation to second axle shaft 226B. At least one pair of bevel pinion gears 272 are meshed with side gears 266A and 266B. Pinions 272 are rotatably supported on a pinion shaft (not shown) in differential housing 250. Power therefore is provided from motor 240 to planetary gear assembly 268 via gearset 242 and to differential gear assembly 248. The fixed connection of planetary carrier 280 to differential housing 250 transmits power to bevel differential gearset 264,which splits and distributes power to axle shafts 226A and 226B, and out to ground engaging wheels 228A, 228B.

[0065] Continuing to refer to FIG. 6 and planetary assembly 268, for proper functionality annulus gear 274 is held against rotation, supported in a manner to counteract loading, and maintains position relative to pinion gears 284. To maintain a simplified axle housing 222, features are included into cover 238 to fully or partially provide support and location of annulus gear 274. Annulus gear 274 is held to prevent rotation relative to axle housing 222, supported in a manner to counteract loading developed within the planetary gears of planetary assembly 268 while maintaining its position and aligned relative to pinion gears 284 and sun gear 278 in an axial direction. A short supportive wall 300 extends from cover 238 and include a circular shaped saddle 302 feature to receive and partially surround the outer diameter of annulus gear 274. Most of saddle 302 is integrated directly into cover 238 without an extensive extending wall portion 300 projecting from the cover 238, because the cover 238 is designed to closely follow the outer diameter of annulus gear 274. Some of the following features described are not visible in FIG. 6, although they are the same features as shown in FIG. 2 and FIG. 4 of the previous embodiment. Reference to these figures in conjunction with the description will allow a full understanding of the concepts presented as applicable for the second embodiment. The rear portion 304 of annulus gear 274 is received into circular shaped saddle 302 of wall 300 and / or cover 238. The forward portion 306 of annulus gear 274 is received into saddle 308 formed as part of axle housing 222. Annulus gear 274 is captured between saddle 302 of cover 238 and saddle 308 of axle housing 222, providing a fully surrounding supporting structure and ensuring the position of the annulus gear 274 is correct relative to the remaining components of planetary assembly 268. An antirotation feature between the outer diameter 310 of annulus gear 274 and axle housing 222 isutilized to ensure annulus gear 274 is fixed for rotation relative to the axle housing 222 and cover 238. The anti-rotation feature, a pair of flats, is arranged as shown and previously described in FIG. 4. Once annulus gear 274 is installed and cover 238 is attached to housing 222, annulus gear 274 is captured and fixed against rotation.

[0066] This arrangement provides a cover assembly 224 that includes a cover 238 with integral features as previously described to support and attach differential assembly 248 and planetary assembly 268 via supporting sun gear shaft 270 to cover 238. Annulus gear 274 is positioned, in a partially supported state by saddle 302, surrounding planetary assembly 268. Such a cover assembly 224 is beneficial because these components can be assembled separate from the remaining portion of axle assembly 220, including the setting of bearing preloads and gear lashes as required. Cover assembly 224 may be installed by inserting the assembly into rear opening 232 of axle housing 222, seating annulus gear 274 into saddle 308. Driven gear 246 will also mesh with drive gear 244. Once cover assembly 224 is fully seated, a plurality of fasteners 240 are installed around cover flange 236 and received by threaded bores in housing flange 234. Axle shafts 226A and 226B may then be inserted axially to connect with side gears 266A and 266B of differential assembly 248.

Claims

CLAIMSWhat is claimed is:

1. An axle assembly comprising: a main axle housing having an opening; an axle cover attached to the main axle housing over the opening, wherein the main axle housing and the axle cover define an internal cavity; a power source having an output; a differential assembly configured to transfer power toward ground engaging wheels; at least one planetary gear assembly operably coupled to the differential assembly; first and second axle outputs configured to drive the ground engaging wheels, wherein the first and second axle outputs are disposed downstream from the at least one planetary gear assembly and the differential assembly in the direction of power transfer from the power source to drive the ground the engaging wheels; wherein the at least one planetary gear assembly and the differential are coaxial with the first and second axle outputs; wherein a differential housing of the differential assembly is rotatable relative to the axle cover; wherein a carrier of the at least one planetary gear assembly is rotatable relative to the axle cover; wherein an annulus gear of the at least one planetary gear assembly surrounds the carrier and is partially received in the axle cover;wherein the at least one planetary gear assembly and the differential assembly are coupled with the axle cover and retained by the axle cover when the axle cover is separate and de-coupled from the main axle housing; wherein the differential assembly and at least one planetary gear assembly are positioned and supported for rotation within said internal cavity by the axle cover, and the annulus gear is captured and rotationally fixed between the main axle housing and axle cover when the axle cover is mounted to the main axle housing.

2. The axle assembly of claim 1, wherein the axle cover includes a plurality of walls extending from the axle cover and formed as one-piece with the axle cover, wherein the walls each define a saddle feature, wherein the at least one planetary gear assembly and the differential housing are mounted on a respective saddle feature and axially located by said respective saddle feature.

3. The axle assembly of claim 2, wherein a plurality of bearings are secured to each of the saddle features between the differential housing and the respective saddle feature and between the at least one planetary gear assembly and the respective saddle feature.

4. The axle assembly of claim 3, wherein a plurality of bearing caps are fastened to each of the walls and combine with the respective walls to circumferentially surround a portion the differential housing and the response bearing and to circumferentially surround a portion of the carrier of the at least one planetary gear assembly and the respective bearing.

5. The axle assembly of claim 4, wherein the bearing caps and walls combine to secure the at least one planetary gear assembly and the differential assembly to the axle housing when the axle housing is separate from the main axle housing.

6. The axle assembly of claim 2, wherein the axle cover defines a cover annulus saddle portion, wherein a first portion of the annulus gear is received in the cover annulus saddle portion, and a second portion of the annulus gear is exposed out from axle cover when the axle cover is separate from the main axle housing7. The axle assembly of claim 6, wherein the annulus gear is fixed against rotation relative to the annulus saddle portion when the axle cover is mounted to the main axle housing.

8. The axle assembly of claim 7, wherein the main axle housing defines a housing annulus saddle portion, wherein the second portion of the annulus gear is received in the housing saddle portion when the axle cover is mounted to the main axle housing.

9. The axle assembly of claim 8, wherein the annulus gear includes a flat outer surface and the main housing includes a flat inner surface on the housing annulus saddle portion, wherein the flat outer surface abuts against the flat inner surface and fixes the annulus gear against rotation when the axle cover is mounted to the main axle housing.

10. The axle assembly of claim 5, wherein the bearings caps and walls each define half circles and define a full circle when mated together.

11. The axle assembly of claim 5, wherein the walls are proud relative to a mounting flange of the cover, wherein the mounting flange corresponds to a housing flange of the main axle housing that surrounds and defines the opening of the main axle housing, such that the walls extend through the opening defined by the main axle housing when the axle cover is mounted to the main axle housing.

12. The axle assembly of claim 1, wherein the power source is a motor, and the motor drives a drive gear, which in meshed engagement with the driven gear that is fixed to the differential housing, wherein the motor and the drive gear are at least partially disposed within main axle housing.

13. The axle assembly of claim 12, wherein the first and second axle outputs are fixed to first and second axle shafts, respectively, wherein the first and second axle shafts drive the ground engaging wheels.

14. The axle assembly of claim 1, wherein the at least one planetary gear assembly includes a first planetary gear assembly and a second planetary gear assembly disposed on opposite axial sides of the differential assembly, wherein the first and second planetary gear assemblies respectively include first and second sun gears, first and second carriers, first and second pluralities of planet gears attached to the first and second carriers and meshed with the first and second sun gears, and first and second annulus gears meshed with the planet gears, wherein the planet gears roll along the annulus gears and rotate the carrier in response to rotation of the sun gear; wherein a first bevel gear of the differential is fixed to the first sun gear;wherein a second bevel gear of the differential is fixed to the second sun gear; wherein the first carrier is fixed to the first axle output; wherein the second carrier is fixed to the second axle output; wherein the power source drives a gear set including a driven gear fixed to the differential housing, wherein rotation of the differential housing transmits power via the differential housing to the bevel gears, wherein rotation of the bevel gears transmits power to the sun gears, wherein rotation of the sun gears transmits power to the first and second axle outputs via the first and second planetary gear assemblies.

15. The axle assembly of claim 14, wherein the first carrier is attached to a bearing held in a saddle of a first carrier wall and captured by a corresponding bearing cap; wherein the second carrier is attached to a bearing held in a saddle of a second carrier wall and captured by a corresponding bearing cap; wherein the first bevel gear is attached to a first differential bearing held in a saddle of a first differential wall and captured by a corresponding bearing cap; wherein the second bevel gear is attached to a second differential bearing held in a saddle of a second differential wall and captured by a corresponding bearing cap; wherein the first annulus gear is disposed axially between the first carrier wall and the first differential wall, wherein a portion of the first annulus gear is held in a saddle formed in the axle housing;wherein the second annulus gear is disposed axially between the second carrier wall and the second differentia wall, wherein a portion of the second annulus gear is held in a saddle formed in the axle housing; wherein the first and second carrier walls are outboard relative to the first and second differential walls; wherein the carrier walls and the differential walls are formed as one-piece with the axle cover, wherein the bearing caps are separate and fixedly fastened to the walls.

16. The axle assembly of claim 1, wherein the at least one planetary gear assembly is a first planetary gear assembly a first axial side of the differential assembly, wherein the first planetary gear assembly includes a first sun gear, a first carrier, a first plurality of planet gears attached to the first carrier and meshed with the first sun gear, and a first annulus gear meshed with the planet gears, wherein the planet gears roll along the annulus gear and rotate the carrier in response to rotation of the sun gear; wherein the first carrier is fixed to the differential housing; wherein a first bevel gear of the differential is fixed to the first axle output; wherein a second bevel gear of the differential is fixed to the second axle output; wherein the power source drives a gear set including a driven gear fixed to the first sun gear, wherein rotation of the first sun gear transmits power to the carrier via the first planetary gear assembly, wherein rotation of the carrier transmits power to the differential housing, wherein rotation of the differential housing transmits power to the bevel gears, wherein rotation of the bevel gears transmits power to the first and second axle outputs.

17. The axle assembly of claim 16, wherein the differential housing is attached to a differential housing bearing held in a saddle of a differential housing wall and captured by a corresponding bearing cap; wherein a shaft of the sun gear is attached to a shaft bearing held in a saddle of a sun gear shaft wall and captured by a corresponding bearing cap; wherein the second bevel gear is attached to a differential bearing held in a saddle of a differential wall and captured by a corresponding bearing cap; wherein the first annulus gear is disposed axially between the sun gear shaft wall and the differential housing wall, wherein a portion of the first annulus gear is held in a saddle formed in the axle housing; wherein the sun gear shaft wall and differential wall are outboard relative to the differential housing wall; wherein the walls are formed as one-piece with the axle cover, wherein the bearing caps are separate and fixedly fastened to the walls.

18. A method of assembling an axle assembly, the method comprising: providing an axle cover having a plurality of walls formed as one-piece with the axle housing, wherein each of the walls extend from the axle cover and define corresponding saddle features; attaching a differential assembly to the axle cover, wherein the differential assembly includes a differential housing rotatably supported in the axle cover and side gears for driving ground engaging wheels;attaching at least one planetary gear assembly to the axle cover, wherein the at least one planetary gear assembly is operatively coupled to the differential gear assembly to transfer torque therebetween; wherein the at least one planetary gear assembly includes an annulus gear meshed with and surrounding a plurality of planet gears attached to a planet carrier, and a sun gear meshed with the planet gears; wherein the at least one planetary gear assembly is coaxial with the differential gear assembly; wherein the differential housing and the at least one planetary gear assembly are attached to bearings received in corresponding saddle features formed in wall portions of the axle cover; attaching bearing caps to the wall portions, wherein the bearing caps combine with the walls portions to fully surround the bearings and retain the differential assembly and the at least one planetary gear assembly to the axle cover, wherein the differential assembly, the at least one planetary gear assembly, and axle cover define an assembled unit; attaching the assembled unit to the main axle housing and receiving the differential assembly and the at least one planetary gear assembly in an interior cavity defined by the main axle housing and the axle cover.

19. The method of claim 18, wherein the annulus gear, as part of the assembled unit, is exposed, wherein the annulus gear is received in a corresponding saddle formed in the main axle housing; wherein the main axle housing includes an inner flat surface that abuts an outer flat surface of the annulus gear and fixes the annulus gear against rotation relative to the main axle housing and the axle cover.

20. The method of claim 18, wherein a drive gear of a power source is disposed within the main axle housing, and the drive gear drivingly engages a driven gear to provide torque to the at least one planetary gear assembly and the differential assembly, wherein the driven gear is fixed to a sun gear of the at least one planetary gear assembly or to the differential housing of the differential assembly.

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