Axle assembly with inboard axle shaft bearings that support a differential mechanism

An axle assembly having a housing, a ring gear received in the housing, a ring gear bearing, a pair of shafts, a differential mechanism and a pair of inboard bearings. The ring gear bearing contacts the housing and the ring gear to support the ring gear for rotation about an axis. The shafts are received in the housing and rotate about the axis. Each of the shafts has a bearing mount and a male splined segment. The differential mechanism has a pair of output members, each of which having a splined internal aperture into which the male splined segment of one of the shafts is slidably received. Each shaft bearing is disposed on the bearing mount of one of the axle shafts and supports the shafts for rotation on the housing. The differential mechanism is supported for rotation about the axis by the ring gear bearing and the inboard bearings.

FIELD

The present disclosure relates to an axle assembly with inboard axle shaft bearings that also support a differential mechanism for rotation relative to an axle housing.

BACKGROUND

Automotive axle assemblies typically include a differential mechanism having a differential case that is supported by a pair of differential bearings for rotation within an axle housing. The differential bearings are typically mounted on trunnions formed on the differential case. The axle shafts of these axle assemblies have an inboard end that is typically engaged to an output member of the differential mechanism and supported indirectly by the differential case. While this type of arrangement is suited for its intended purpose, there remains a need in the art for an improved bearing arrangement that supports the axle shafts and the differential mechanism.

SUMMARY

In one form, the present teachings provide an axle assembly that includes a housing, a ring gear received in the housing, a ring gear bearing, a pair of axle shafts, a differential mechanism and a pair of inboard axle shaft bearings. The ring gear bearing contact the housing and the ring gear and supports the ring gear for rotation about an axis relative to the housing. The axle shafts are received in the housing and are rotatable about the axis. Each of the axle shafts has an end with a bearing mount and a male splined segment. The differential mechanism has a pair of output members, each of which having a splined internal aperture into which the male splined segment of one of the axle shafts is slidably received. Each inboard axle shaft bearing is disposed on the bearing mount of a corresponding one of the axle shafts and supports the corresponding one of the axle shafts for rotation on the housing. The differential mechanism is supported for rotation about the axis by the ring gear bearing and the inboard axle shaft bearings.

DETAILED DESCRIPTION

With reference toFIG. 1of the drawings, an exemplary vehicle having an axle assembly (e.g., a rear axle assembly) constructed in accordance with the teachings of the present disclosure is generally indicated by reference numeral10. The vehicle10can have a power train12and a drive line or drive train14. The power train12can be conventionally constructed and can comprise a power source16and a transmission18. The power source16can be configured to provide propulsive power and can comprise an internal combustion engine and/or an electric motor, for example. The transmission18can receive propulsive power from the power source16and can output power to the drive train14. The transmission18can have a plurality of automatically or manually-selected gear ratios. The drive train14in the particular example provided is of a two-wheel, rear-wheel drive configuration, but those of skill in the art will appreciate that the teachings of the present disclosure are applicable to other drive train configurations, including four-wheel drive configurations, all-wheel drive configurations, and front-wheel drive configurations. The drive train14can include a prop shaft20and a rear axle assembly22. The propshaft20can couple the transmission18to the rear axle assembly22such that rotary power output of the transmission18is received by the rear axle assembly22. The rear axle assembly22can distribute the rotary power to the rear vehicle wheels26.

With reference toFIG. 2, the rear axle assembly22can include a housing30, an input pinion32, a ring gear34, a differential assembly36, and a pair of axle shafts38(only one is shown). The input pinion32can be rotatable about a first axis40, while the ring gear34and the differential assembly36can be rotatable about a second axis42that can be transverse (e.g., perpendicular) to the first axis40.

The housing30can define a differential cavity50into which the differential assembly36can be received. The input pinion32can be received in the differential cavity50and can include a plurality of pinion teeth52.

The ring gear34can be received in the differential cavity50and can include a plurality of ring gear teeth60that are meshingly engaged to the pinion teeth52. An angular contact bearing70can support the ring gear34for rotation on the housing30about the second axis42. The angular contact bearing70can have a first race72, which can be integrally formed (i.e., machined) into the ring gear34, a second race74, which can be defined by one or more race members, and a plurality of bearing balls76that can be disposed between the first and second races72and74.

The differential assembly36can comprise a differential case100, a pair of output members102, and a means104for permitting speed differentiation between the output members102. The differential case100can have a case body110, one or more end caps112and one or more end cap securing structures114. In the example provided, the case body110has a generally tubular body member116, a radial flange member118, and a circumferential gusset120. The case body110can define a case cavity124that can be configured to receive the speed differentiation means104. The radial flange member118can extend about the case body110and can extend radially outwardly therefrom. The radial flange member118can be configured to be coupled to the ring gear34, for example via one or more welds. In the example provided, however, the case body110is formed of aluminum and a plurality of bolt holes130are formed through the radial flange member118; the bolt holes130are configured to receive threaded bolts132therethrough that are threadably engaged to the ring gear34. The circumferential gusset120can be formed on a side of the radial flange member118that is opposite the ring gear34and can connect the radial flange member118to the case body110in a manner that resists deflection of the radial flange member118and the ring gear34in a direction away from the input pinion32in response to the transmission of forces transmitted to the ring gear34when the teeth52of the input pinion32meshingly and drivingly engage the teeth60of the ring gear34. It will be appreciated, however, that other means may be employed to resist deflection of the ring gear34in the direction away from the input pinion32in response to the transmission of forces transmitted to the ring gear34when the teeth52of the input pinion32meshingly and drivingly engage the teeth60of the ring gear34. For example, a thrust bearing140can be additionally or alternatively disposed between the housing30′ and either the ring gear34′ or the differential case100′ as is shown inFIG. 3.

Returning toFIG. 2, it will be appreciated that since the differential case100is fixedly coupled to the ring gear34for rotation therewith, conventional bearings for directly supporting the differential case100for rotation on the housing30are not required (but may be provided if desired).

One or more of the end caps112can be provided to permit the assembly of the speed differentiation means104into the case cavity124in the case body110and to close a respective end of the case cavity124. In the example provided, a first end cap112ais an annular structure that is integrally formed with and extends radially inwardly from the case body110, while a second end cap112bcan be an annular structure that is slidably received into the case cavity124. The end cap securing structure114is employed to limit outboard movement of the second end cap112balong the second axis42. In the particular example provided, the end cap securing structure114comprises a snap ring150that is received into a circumferentially extending groove152that is formed in the case body110, but it will be appreciated that other types of devices, including threaded fasteners or clips, could be employed in the alternative.

The output members102can be rotatably disposed about the second axis42. The speed differentiation means104can comprise any means for permitting speed differentiation between the output members102. For example, the speed differentiation means104can include one or more clutches, such as friction clutches (not shown), that can be operated to permit/control speed differentiation between the output members102. Alternatively, the speed differentiation means104can comprise a differential gearset160. In the particular example provided, the differential gearset160comprises a cross-pin162, a pair of differential pinions164(only one shown) and a pair of side gears166that are co-formed with the output members102, but it will be appreciated that the differential gearset160could be constructed differently. The cross-pin162can be mounted to the differential case100and can be disposed generally perpendicular to the second axis42. The differential pinions164can be rotatably mounted on the cross-pin162and can be meshingly engaged with the side gears166. The side gears166can be retained in the case cavity124via the first and second end caps112aand112b. Each of the output members102can be fixedly and non-rotatably coupled to an associated one of the side gears166and can define an internally splined aperture170.

Each of the axle shafts38can have an inboard end180with a bearing mount182and a male splined segment184. The male splined segment184can be received into the internally splined aperture170in one of the output members102to thereby axially slidably but non-rotatably couple each axle shaft38to an associated one of the output members102. An inboard axle shaft bearing190can be mounted on the bearing mount182and the housing30to thereby directly support the inboard end180of the axle shaft38for rotation on the housing30. It will be appreciated that the differential case100can be supported for rotation about the second axis42relative to the housing30via the ring gear bearing70and the inboard axle shaft bearings190and that the rear axle assembly22need not employ any bearings to directly support the differential case100for rotation on the housing30.

The rear axle assembly22can include a pair of first retention mechanisms200(only one of which is shown), each of which being coupled to an associated one of the axle shafts38and being configured to limit movement of the axle shafts38along the second axis42in an outboard direction. The first retention mechanism200can comprise a wedding band202that can be fixedly mounted (e.g., press-fit or shrunk-fit) on the inboard end180of the axle shaft38axially between the inboard axle shaft bearing190and the output member102. The wedding band202can be configured to abut the inboard axle shaft bearing190to limit movement of the axle shaft38along the second axis42in a direction away from an associated one of the output members102. Optionally, the wedding bands202could be employed to preload the inboard axle shaft bearings190. In this regard, the wedding bands202could be driven in an outboard direction along the inboard ends180to preload the inboard axle shaft bearings190and can be fixed thereon so as to maintain a desired preload on the inboard axle shaft bearings190. It will be appreciated that contact between one of the wedding bands202and one of the inboard axle shaft bearings190will limit outboard axial movement of an associated one of the axle shafts38.

Optionally, the rear axle shaft22can further comprise a pair of second retention mechanisms210, each of which being configured to limit movement of a corresponding one of the axle shafts38in an outboard axial direction. In one form, each of the second retention mechanisms210can comprise a retaining ring212that can be received into a circumferentially-extending slot214that can be formed on the inboard end180of the corresponding one of the axle shafts38axially between the wedding band202and the output member102. The slot214can be formed into any desired portion of the inboard end180, such as in the male splined segment184.

Alternatively, each of the second retention mechanisms210acould comprise a clip220that can be assembled to the inboard end180of the corresponding one of the axle shafts38aas shown inFIG. 4. The clip220could be configured to protrude from one or more holes224in the inboard end180of the axle shaft38a. In the example provided, the inboard end180of the axle shaft38ais hollow, the clip220has a U-shaped body226, which is received into the hollow inboard end180, and a pair of ears228(only one shown) that extends outwardly from the U-shaped body226. The ears228extend out of the holes224, which are formed radially through the inboard ends180and which intersect the hollow interior of the axle shafts38a. The ears228of each clip220can be disposed in-line with a corresponding one of the wedding bands202. It will be appreciated that in the event that the wedding band202is de-coupled from (and axially slidable on) the inboard end180of a corresponding one of the axle shafts38a, the wedding band202may move in an axially inboard direction relative to the axle shaft38auntil it is halted through contact with the ears228(which are abutted against the surface of the holes224). The holes224can be formed in any desired location, such as into the male splined segment184.

InFIG. 5, an alternative second retention mechanism210bis illustrated. The second retention mechanism210bcomprises a nut240that can be threaded onto a portion of the inboard end180bof the axle shaft38band abutted against the wedding band202. A clamping force generated by the nut240can lock the nut240to the axle shaft38bso as to resist relative rotation there between. If desired, a portion244of the nut240can be permanently (plastically) deformed to resist rotation of the nut240relative to the inboard end180bof the axle shaft38b. In the example provided, the portion244of the nut240is deformed into a space between circumferentially spaced apart splined teeth on the externally splined segment184b. In this regard, one of the splines on the externally splined segment184bcan be omitted so that there is a relatively large space between the male spline teeth that is adapted to receive the permanently deformed portion244of the nut240.

Alternatively, the nut240can be employed as the first retention mechanism200. In this example, the nut240is abutted directly against inboard axle shaft bearing190and if desired, a clamping force generated by the nut240can lock the nut240to the axle shaft38bso as to resist relative rotation there between. If desired, the portion244of the nut240can be permanently (plastically) deformed to resist rotation of the nut240relative to the inboard end180bof the axle shaft38b.

With additional reference toFIG. 6, a separate and discrete anti-rotation structure250could be assembled to the nut240and to the axle shaft38brather than deforming the nut240as was described in the above two examples. In this example, the anti-rotation structure250comprises a structure body252, an internally splined aperture254, which is formed through the structure body252and configured to meshingly engage the male splined segment184bof the inboard end180bof the axle shaft38b, and one or more clip members256that can extend from the structure body252and are configured to resiliently engage a flat F on the nut240to thereby inhibit rotation of the nut240relative to the anti-rotation structure250.

InFIG. 7, the axle shaft38is illustrated as being a weldment that is formed of a generally tubular portion270and a wheel flange272. At least a portion of the axle shaft38, such as the generally tubular portion270, can be formed of a suitable steel material, such as a steel material having a carbon content that is less than or equal to 0.35% by weight, and can be heat treated to have a surface hardness that is greater than or equal to 45 Rockwell C. The steel material can be any desired steel material, such as a moderate strength low-alloy or plain carbon steel material (e.g., A.I.S.I. 1030 steel), that can provide fair or better machine-ability, ductility and weld-ability. It will be appreciated that selection of an appropriate steel material (e.g., by carbon content) can also serve to limit the maximum possible hardness that is obtained during heat treatment of the axle shaft38.

The wheel flange272can include a tubular segment276that can be welded to the generally tubular portion270in a suitable process, such as friction welding. If desired, the wheel flange272can define a first joint member280, an annular weld cavity282and a containment lip284. The first joint member280can be configured to be fixedly coupled to a second joint member290formed on the generally tubular portion270and as such, the first joint member280can have a generally tubular shape that can be sized (outside diameter and inside diameter) in a manner that is similar to the portion of the generally tubular portion270that defines the second joint member290. The annular weld cavity282can be formed concentrically about the first joint member280and can be positioned and sized to provide space for extruded portions294and296of the first and second joint members280and290, respectively, that are created during the friction welding process. The containment lip284can extend radially inwardly from a remaining portion of the wheel flange272and can terminate in relatively close proximity to the second joint member290. During the (rotary) friction welding process, the first and second joint members280and290are abutted against one another and heat is generated by friction as one of the first and second joint members280and290is rotated relative to and advanced toward the other one of the first and second joint members280and290. When sufficient material has been extruded from the first joint member280and/or the second joint member290, relative rotation can be halted and the one of the first and second joint members280and290can be advanced toward the other one of the first and second joint members280and290to form the friction weld W (i.e., to forge the first and second joint members280and290together). The extruded portions294and296of the first and second joint members280and290can be received within the annular weld cavity282. Moreover, the extruded portions294and296are sized so that they are disposed in-line with the containment lip284. Accordingly, it will be appreciated that were the first joint member280or the friction weld W to fail, contact between the containment lip284and the extruded portion296of the second joint member290would inhibit movement of the wheel flange272in an outboard direction along the second axis42relative to the generally tubular portion270.