Support structure for differential

A support structure for a differential assembly comprising: a support ring having a peripheral wall extending between a first face and a second face, the support ring having a non-hollow center; a bore in the peripheral wall sized and shaped to receive a pinion shaft; and an aperture in the first face, the second aperture in fluid communication with the first aperture.

FIELD OF THE INVENTION

The present invention generally relates to mechanical differentials, and more particularly to a support structure for supporting one or more pinion shafts in a mechanical differential.

BACKGROUND OF THE INVENTION

Differential assemblies are known in the automotive industry as devices that split engine torque two ways, allowing each output to spin at a different speed. Generally, differential assemblies have three primary tasks: to aim the engine power at the wheels; to act as the final gear reduction in the vehicle, slowing the rotational speed of the transmission one final time before transmission to the wheels; and to transmit the power to the wheels while allowing them to rotate at different speeds.

A typical mechanical differential contains a housing (or carrier), two side gears, and several pinion gears. A rotating driveshaft of the vehicle engages a ring gear, which is mounted onto the differential housing. The driveshaft drives the ring gear, which in turn rotates the differential housing. Pinion shafts attach the pinion gears to the housing so that, as the housing rotates, the pinion gears are driven. The pinion gears drive the two side gears, which in turn drive the axle (or half shafts) attached thereto.

The pinion shafts of the differential assembly typically have a support ring that secures to the inward ends of pinion shafts so that the torque of the housing can be transmitted to the pinion shafts and thereby drive the pinion gears. The pinion gears spin upon the pinion shafts and rotate about the axis of the housing.

The conventional support ring is typically a ring-type component having a hollow center with a plurality of apertures provided through the wall of the support ring for receiving the ends of the pinion shafts. This type of support ring is usually made from a hollow tube or pipe. In some cases, the required size of the support ring does not correspond to the size of the standardized tube material supplied in the market. In such cases, manufacturers have been forced to use solid bars that correspond to the required size of the support ring. However, solid bars generally have to be substantially machined to create rings. As such, a large amount of material has to be machined to form a hollow support ring having the required dimensional characteristics.

With reference toFIGS. 1A and 1B, typical mechanical differentials contain a housing1, two side gears3, and several pinion gears4. The pinion gears4are fixed to the housing1by a pinion shaft5so that the pinion gears4may be driven by the housing1to rotate around the housing1while spinning on the pinion shafts5. Typically, the pinion shafts5are rigidly secured to the housing1at their respective distal ends, and supported by a support ring6at their respective proximal ends. Torque is transmitted to the housing1, and the housing1drives the pinion shafts5which in turn drives the pinion gears4. As the pinion gears4move, the pinion gears4drive the side gears3so that torque may be transmitted to the side gears3.

FIGS. 2A-2Eillustrates a conventional support ring6having an outer surface11and inner surface13, with the inner surface13defining a hollow center. Typically, three apertures10are machined through the outer surface11and the inner surface13of the support ring6to provide connections for the pinion shafts.

During operation of the differential assembly, friction and heat are generated as components within the differential housing are engaging and contacting one another. This friction and heat reduces the durability and load carrying capacity of the differential assembly, such as by causing scoring damage to the contact surfaces. Consequently, in most applications, the differential assembly must guide lubricant to the various frictional surfaces to relieve friction and minimize the generation of heat.

For example, the contact surfaces of the pinion gear bore and pinion shaft5are among the important surfaces that require significant lubrication. In many applications, the lubricant for lubricating these surfaces is supplied to the differential through shaft bores17and corresponding splined bores18of the side gears3. Under the effect of centrifugal force generated when the differential is rotating, the lubricant flows inwardly thru the shaft bores17and splined bores18, and the lubricant is collected by the inner surface13of support ring6. The lubricant then flows through the clearance between the bores10of the support ring6and flat features19of each pinion shaft5to a corresponding interface of the contact pair of the pinion gear bore and pinion shaft5.

Consequently there exists a significant need for a pinion shaft support structure that is capable of providing lubrication pathways to the interface of the pinion gear bores and pinion shafts, while also capable of reducing the time and expense in machining the support structure thereby resulting in reduced manufacturing costs.

DETAILED DESCRIPTION

While the present support structure is described with reference to several embodiments described herein, it should be clear that the present invention should not be limited to such embodiments. Therefore, the description of the embodiments provided herein are illustrative of the present invention and should not limit the scope of the invention as claimed.

Reference will now be made in detail to an embodiment of the invention as illustrated in accompanyingFIGS. 3A-3E. In accordance with the embodiment, a support structure20is generally illustrated. For example, the support structure20may consist of a support ring22capable of use in a differential assembly. The shape of the support ring22should not be deemed as limited to any specific shape. The support ring22may correspond to the shape of the differential housing, for example.

In an embodiment, the support ring22may generally be manufactured from a rod material, such as a non-hollow bodied metal rod material. Use of the non-hollow rod material can provide manufacturing cost savings, especially when used to manufacture the support rings22having required dimensions different from typical hollow, rod dimensions and similar to the dimensions of non-hollow rod dimensions. In such an embodiment, the present invention permits a reduced amount of machining and, as a result, a cost savings.

As shown inFIGS. 3A-3E, the support ring22may comprise an outer wall24and an inner wall25extending between faces28of the sidewalls26. In an embodiment, the support ring22may be annular and cylindrical. The faces28may be recessed, such as by machining the faces28a predetermined distance within the sidewalls26. For example, a non-hollow tube material may be cut into sections to form the support ring22, and the faces28may be machined into the sidewalls26. One of ordinary skill in the art will appreciate other methods for forming the recessed sidewalls26, including but not limited to casting, such as die casting.

A plurality of bores30may be machined into the outer wall24so that the inner ends of a plurality of pinion shafts, such as pinion shafts5shown inFIGS. 4A and 4B, may be supported therein. The bores30are machined such that the bores30extend a predetermined distance within the support ring22, such as a predetermined distance toward the center of the support ring22. The dimensions of the bores30may correspond to and/or may be substantially similar to the pinion shafts that may be supported therein. For example, in order to support cylindrical pinion shafts, the bores30may be circular and have at least a diameter equal to the pinion shafts5.

Windows (or apertures)32may be formed in the faces38of the support ring22. The windows32may permit fluid communication with the faces28and the bores30. The windows32may be smaller in size than the bores30. It should be realized that the configuration of the support structure20, or any features thereof, may be machined from a solid or non-hollow body of any suitable shape or material; alternatively, the support structure20, or any features thereof, may be molded from powdered metal, a durable polymer, a composite material, or the like. Additionally, while the illustrative embodiment shows three bores30for supporting three pinion shafts5, it will be appreciated that any number of apertures for supporting any number of pinion shafts may be utilized.

The windows32may be cut into or otherwise formed into the faces28of the support ring22such that lubricant coming from the center holes of the side gears3may flow into the faces28and into the bores30to reach the pinion shafts5. For example, if the support ring22is incorporated into the differential housing1ofFIGS. 4A and 4B, centrifugal force of the components of the differential housing1along with the surface tension of the lubricant may aid in permits lubricant to flow through the bores30and on the pinion shafts5. Lubrication of the pinion shafts5is typically needed or at least desirable between the inner bore of the pinion gears and pinion shafts5. The windows32may be used to aid in removing or assembling the pinion shafts5from or into the support structure20.

One of ordinary skill in the art will appreciate various methods for manufacturing the support ring22. For example, one method may involve providing a non-hollow material, cutting the material into a desired thickness defined between the sidewalls26, and machining the faces28into the sidewalls26. In another embodiment, the support ring22may be cast into the desired thickness as a non-hollow material. In such an embodiment, if it is desired to have the faces28recessed into the sidewalls26, recesses may be machined into the sidewalls26or the faces28may be cast in such a manner. One or more of the bores60and one or more of the windows32may be machined, cast or otherwise formed into the outer wall24of the support ring22.

FIGS. 5 and 6illustrate an alternative embodiment of a support structure100. The support structure100comprises a generally non-hollow body105having side walls120extending between an inner wall135and an outer wall110. The side walls120may have faces130, which may be recessed toward the opposing sidewall120. The outer wall110may include one or more bores140, each capable of supporting the proximal end of a corresponding pinion shaft5.

The faces130may have one or more apertures (or windows)150for providing fluid communication to the bores140. While the apertures150are illustrated as having circular cross-sections, it should be appreciated that any suitable cross-sectional shape may be employed, including but not limited to triangular, square, rectangular, hexagonal, octagonal, or the like. A hole160may also be included in the faces130to assist in the assembly and disassembly of the differential. In an embodiment, the hole160may be used similar to the apertures150, preferably only if the hole150terminates within the body of the support structure100.

It should be realized that the configuration of the support structure100, or any features thereof, may be machined from a non-hollow body of any suitable shape or material; alternatively, the support structure100, or any features thereof, may be molded from powdered metal, a durable polymer, a composite material, or the like. Additionally, while the illustrative embodiment shows three bores140for supporting three pinion shafts5, it will be appreciated that any number of apertures for supporting any number of pinion shafts may be utilized.

Referring again toFIGS. 5 and 6, the apertures150permit lubrication coming from the center holes of the side gears3to flow from the annular pockets130to the pinion shafts5. With the help of centrifugal force and surface tension, the lubricant may flow along the pinion shafts5into the interface between the inner bore of the pinion gears and pinion shafts to improve lubrication therebetween.

The invention has been described above and, obviously, modifications and alternations will occur to others upon a reading and understanding of this specification. The claims as follows are intended to include all modifications and alterations insofar as they come within the scope of the claims or the equivalent thereof.