Flow-formed differential case assembly

A differential case assembly includes a differential case and an integral end cap and ring gear assembly. The differential case has an open end and a side wall with an exterior surface. The integral end cap and ring gear assembly is disposed over the open end of the differential case and adjacent the exterior surface. A first interior portion of the integral end cap and ring gear assembly abuts the exterior surface of the differential case to define a weld joint interface. The integral end cap and ring gear assembly is configured to permit a welding operation at the weld joint interface.

FIELD OF THE INVENTION

The present disclosure relates to a differential case assembly and, more particularly, to a differential case assembly for use in a motorized vehicle.

BACKGROUND OF THE INVENTION

A differential is a device, usually employing gears, that is capable of transmitting torque and permitting rotation of different shafts at different speeds. Known differentials have cases that are cast from metals such as iron, and are often heavy and volumetrically undesirable. Assembly of known differentials can be difficult, oftentimes requiring bolting as well as welding. The use of “feed-in and rotate processes” when cast iron differential cases are manufactured is also known. Welding of the differentials formed from cast iron, in particular, can undesirably require the use of filler wire to provide an acceptable weld.

A particular differential case assembly is described in Assignee's co-pending U.S. Patent Application Publication No. 20110263374 to Cripsey, filed on Apr. 26, 2011, the entire disclosure of which is hereby incorporated herein by reference. The differential case assembly includes a differential case having an open end and a side wall with an interior surface, A plurality of major internal splines is formed on the interior surface of the side wall. The differential case assembly further includes a gear assembly. The gear assembly has a retainer insert and a cross pin. The retainer insert is disposed adjacent the interior surface of the side wall between a pair of the major internal splines. The retainer insert has a hole formed therein. The cross pin has an end mounted in the hole of the retainer insert. The cross pin aligns the gear assembly within the differential case.

There is a continuing need for a differential case assembly that is lighter compared to known cast iron designs, minimizes a required packaging space, minimizes assembly complexity, and can be employed with different numbers of gears. A differential case assembly that facilitates welding and eliminates a need for multiple nuts/bolts in the assembly process is also desired.

SUMMARY OF THE INVENTION

In concordance with the instant disclosure, a differential case assembly that is lighter compared to known cast iron designs, minimizes a required packaging space, minimizes assembly complexity, can be employed with different numbers of gears, facilitates welding, and eliminates a need for multiple nuts/bolts in the assembly process, is surprisingly discovered.

In one embodiment, a differential case assembly includes a differential case and an integral end cap and ring gear assembly. The differential case has an open end and a side wall with an exterior surface. The integral end cap and ring gear assembly is disposed over the open end of the differential case and adjacent the exterior surface. A first interior portion of the integral end cap and ring gear assembly abuts the exterior surface of the differential case to define a weld joint interface. A second interior portion of the integral end cap and ring gear assembly is spaced apart from the exterior surface and defines a void therebetween. The void permits a welding operation of the differential case to the integral end cap and ring gear assembly at the weld joint interface.

In another embodiment, a differential case assembly includes a differential case and an integral end cap and ring gear assembly. The differential case has an open end and a side wall with an exterior surface. The integral end cap and ring gear assembly is disposed over the open end of the differential case and adjacent the exterior surface. A first interior portion of the integral end cap and ring gear assembly abuts the exterior surface of the differential case to define a weld joint interface. The integral end cap and ring gear assembly has a plurality of slots formed therein that permit access to both the differential case and the integral end cap and ring gear assembly for a welding operation at the weld joint interface.

In a further embodiment, a method for manufacturing a differential case assembly includes the steps of: providing a differential case having an open end and a side wall with an exterior surface; and disposing an integral end cap and ring gear assembly over the open end of the differential case and adjacent the exterior surface. A first interior portion of the integral end cap and ring gear assembly abuts the exterior surface of the differential case to define a weld joint interface. The integral end cap and ring gear assembly further includes at least one of a second interior portion spaced apart from the exterior surface and defining a void therebetween, and a plurality of slots. Each of the void and the slots permits a welding operation of the differential case to the integral end cap and ring gear assembly at the weld joint interface. The method further includes the step of welding the differential case with the integral end cap and ring gear assembly at the weld joint interface.

DETAILED DESCRIPTION OF THE INVENTION

The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should also be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. In respect of the methods disclosed, the order of the steps presented is exemplary in nature, and thus, is not necessary or critical.

FIGS. 1-8depict a differential case assembly2according to the present disclosure. The differential case assembly2advantageously permits a welding operation from at least one of from “below” the differential case assembly2(FIGS. 1-4) and “above” the differential case assembly (FIGS. 5-8), as desired.

The differential case assembly2includes a differential case4, an end cap6, a ring gear8, and a gear assembly10. The differential case4, the end cap6, and the ring gear8cooperate to house the gear assembly10. It should be understood that the gear assembly10may have a cross pin, for example, as disclosed in Assignee's co-pending U.S. patent application Ser. No. 13/094,406, or may be pinless, for example, as disclosed in Assignee's co-pending pending U.S. patent application Ser. No. 13/174,971, the entire disclosures of which are hereby incorporated herein by reference.

As shown inFIG. 3, the differential case4has an open end12and a side wall14with an exterior surface16. In a nonlimiting example, the differential case4is a flow formed shell. Skilled artisans should appreciate that the flow forming process for manufacturing the differential case4results in a plastic deformation of the preform and a non-interrupted grain flow for the formed differential case4. Through plastic deformation, the preform material undergoes work hardening and can become stronger than the original preform material. The flow formed differential case4furthermore has minimal porosity and can be made thinner by wall reduction, and significantly lighter in comparison to cast iron differential case assemblies known in the art. Other methods for forming the differential case4may also be used, as desired

The end cap6and the ring gear8may be provided as a one piece, integral end cap and ring gear assembly6,8. The integral end cap and ring gear assembly6,8are disposed over the open end12of the differential case4and adjacent the exterior surface16of the side wall14. For example, the integral end cap and ring gear assembly6,8may have an outwardly extending edge portion that permits the integral end cap and ring gear assembly6,8to be placed over top of the differential case4, while also disposing the outwardly extending edge portion adjacent the side wall14of the differential case4. The integral end cap and ring gear assembly6,8may be cold formed or hot formed, or formed by another suitable process, within the scope of the present disclosure.

With reference toFIGS. 1-4, the integral end cap and ring gear assembly6,8has a first interior portion18and a second interior portion20. The first interior portion18of the integral end cap and ring gear assembly6,8abuts the exterior surface16of the differential case4. For example, a portion of the exterior surface16that abuts the first interior portion18of the integral end cap and ring gear assembly6,8may be defined by an outwardly extending lip21of the differential case4adjacent the open end12of the differential case4. Other means for defining the portion of the exterior surface16that abuts the first interior portion18may also be used, as desired.

The abutting of the exterior surface16and the first interior portion18defines a weld joint interface22of the differential case assembly2. The second interior portion20of the integral end cap and ring gear assembly6,8is spaced apart from the exterior surface16. The second interior portion20and the exterior surface16together define a void24therebetween. The void24permits the welding operation of the differential case4to the integral end cap and ring gear assembly6,8from “below” the differential case assembly2, at the weld joint interface22.

As illustrated inFIGS. 3 and 4, it has been surprising found that having the weld joint interface22be disposed along a plane A facilitates the welding operation of the weld joint interface22. The plane A is oriented at an acute angle relative to a vertical plane V. As such, the weld joint interface22is angled or tapered and permits the integral end cap and ring gear assembly6,8to be pressed into the differential case4during assembly. A surface of the second interior portion20of the integral end cap and ring gear assembly6,8may also be parallel with the plane A, for the purpose of facilitating welding access to the weld joint interface22.

As a nonlimiting example, the vertical plane V may be substantially parallel to exterior surface16of the side wall14adjacent the second interior portion20of the integral end cap and ring gear assembly6,8. The angle may particularly be up to about 15 degrees, more particularly between about 5-10 degrees, and most particularly about 7.5 degrees. One of ordinary skill in the art may select other suitable angles for the acute angle of the plane A, as desired.

Referring further toFIGS. 3 and 4, it is also surprisingly found that the welding operation is facilitated where a base26of the lip21is disposed on a plane B. The plane B is oriented orthogonal to the plane A of the portion of the exterior surface16that abuts the first interior portion18of the integral end cap and ring gear assembly6,8. Where a means for welding such as a laser is used for the welding operation, and the means for welding is oriented along the plane A, in line with the weld joint interface22, the base26being disposed on the plane B results in a more consistent heating and welding at the weld joint interface22.

As also shown inFIGS. 3 and 4, the differential case assembly2may further include a minor void30at the weld joint interface22. In particular, the minor void30is disposed between exterior surface16of the side wall14of the differential case4and the first interior portion18of the integral end cap and ring gear assembly6,8. The minor void30may be defined by grooves formed in at least one of the exterior surface16and the first interior portion18. The minor void30permits a collection of gases that may be generated during the welding operation, and facilitates the formation of a superior weld at the weld joint interface22.

Referring now toFIGS. 5-8, the differential case assembly2of the present disclosure may also permit the welding operation from “above” the differential case assembly2. The welding operation may be performed through a plurality of slots32that are formed in the integral end cap and ring gear assembly6,8. For example, the slots32may permit access to both the differential case4and the integral end cap and ring gear assembly6,8for the welding operation. The slots32are also spaced apart, which results in a series of stitch-type or intermittent welds during the welding operation.

In a particular embodiment illustrated inFIGS. 7 and 8, a ledge34is formed in the integral retaining cap and ring gear assembly6,8. The ledge34exposes the weld joint interface22beneath each of the slots32. In certain embodiments, the ledge34provides an outer half of the weld joint interface22exposed beneath each of the slots32. Where the weld joint interface22is exposed thusly, it should be appreciated that the welding operation may be performed from “above” the differential case assembly2. The welding operation from “above” may be performed together with, or separate from, the welding operation performed from “below” on the differential case assembly2.

The present disclosure also includes a method for manufacturing the differential case assembly2. The method first includes the steps of providing the differential case4and disposing the integral end cap and ring gear assembly6,8over the open end12of the differential case4and adjacent the exterior surface16of the side wall14of the differential case4. The disposing of the integral end cap and ring gear assembly6,8over the open end12of the differential case4results in an abutting of the differential case4and the integral end cap and ring gear assembly6,8, and the subsequent formation of a weld joint interface22.

The differential case assembly2may be configured for at least one of the “below” welding operation and the “above” welding operation at the weld joint interface22, as described hereinabove. Accordingly, the method for manufacturing the differential case assembly2further includes the step of welding the differential case4with the integral end cap and ring gear assembly6,8at the weld joint interface22, either through the void24below the weld joint interface22or through the slots32above the weld joint interface22.

In particular embodiments, the welding operation is a laser welding operation. However, one of ordinary skill in the art may select other suitable means for welding during the welding operation, as desired.

Advantageously, the differential case assembly2of the present disclosure is less massive and more volumetrically efficient than differentials for motorized vehicles that are known in the art. Furthermore, the differential case assembly2may be manufactured without the use of screws, bolts, rivets, or the like.