Method of forming a constant velocity joint

The present invention is directed to a constant velocity joint (“CV joint”) and, more particularly, to a Rzeppa CV joint and method of forming the same. The method generally includes the steps of forming a bell shaped outer bearing race and separating the bell shaped outer bearing race into a disc shaped outer bearing race and a stub shaft. The method may further include the step of machining the bell shaped outer bearing race to create the stub shaft integrally connected to the disc shaped outer bearing race, before separating the bell shaped outer bearing race into the disc shaped outer bearing race and the stub shaft.

BACKGROUND OF THE INVENTION

The present invention is directed to a constant velocity joint (“CV joint”) and method of forming the same.

Two types of Rzeppa CV joints are commonly used in vehicles. The first type is a bell shaped CV joint and the second type is a disc shaped CV joint. The bell shaped CV joint is formed with a bell shaped outer bearing race having a bell shaft protruding from the crown of the bell. The bell and bell shaft are generally aligned symmetrically about a bell axis. Reference points may be forged on the bell and bell shaft for locating the bell axis during machining. The reference points allow precise and accurate machining of the bell shaped outer bearing race to provide a well balanced outer bearing race about the bell axis.

Disc shaped CV joints typically include a disc shaped outer bearing race, an inner bearing race, and stub shaft having a hub on one end. Alternatively, the disc shaped CV joint may be formed without the stub shaft and instead be flange mounted to a shaft. When assembled, the inner race fits within the outer disc race, with ball bearings located therebetween. A splined portion of the stub shaft then fits within the inner bearing race, specifically a splined hub on the inner bearing race. The CV joint provides articulation by the outer bearing race, connected to one shaft of the driveshaft, articulating relative to the inner bearing race and stub shaft, connected to the other shaft of the driveshaft. The outer bearing race and stub shaft are separately forged with each having their own axis. Therefore, during machining, the outer bearing race and stub shaft are machined about their respective axes, which may not be in alignment when assembled into a CV joint. To provide a CV joint with minimal noise, vibration, and harshness issues, the axes should be in alignment with one another when assembled and in alignment with the axis of the assembled CV joint. Another problem with disc shaped CV joints is that they are typically difficult to precisely and accurately manufacture, because each part is separately formed and machined. Other problems include finding the axis of each part during the machining process, especially the disc shaped outer bearing race. Each of the above problems makes it difficult to efficiently machine and assemble the CV joint so that the axes of each part are aligned and balanced to reduce or eliminate noise, vibration, and harshness issues. Another problem with disc type CV joints is that it currently is not possible to efficiently and repeatedly form the outer disc bearing race to near net shape tolerances so that the amount of machining is limited, especially machining of bearing races.

SUMMARY OF THE INVENTION

The present invention is directed to a constant velocity joint (“CV joint”) and, more particularly, to a Rzeppa CV joint and method of forming the same. The method generally includes the steps of forming a bell shaped outer bearing race and separating the bell shaped outer bearing race into a disc shaped outer bearing race and a stub shaft. The method may further include the step of machining the bell shaped outer bearing race to create the stub shaft integrally connected to the disc shaped outer bearing race, before separating the bell shaped outer bearing race into the disc shaped outer bearing race and the stub shaft.

The bell shaped outer bearing race may include a bell axis, an outer surface and a first face and the step of machining the bell shaped outer bearing race may further include the step of creating reference datums on at least one of the outer surface and first face of the integrally coupled stub shaft and disc shaped outer bearing race. The step of machining the bell shaped outer bearing race may also includes the step of using a reference point and an outer bearing recess and/or a cage track to determine the bell axis. Splines, snap ring grooves and boot grooves may also be formed on the stub shaft.

The method of forming a constant velocity joint may also include the steps of, forming a bell shaped outer bearing race having a housing defining a cavity, a crown, and a bell shaft extending from said crown, and separating the housing defining a cavity from the crown and the bell shaft. The bell shaped outer bearing race may further include a bell axis, a first reference point defined by at least one of the crown and the bell shaft, a cage track and an outer bearing recess, and wherein the method further includes the step of machining the bell shaped outer bearing race about the bell axis using the reference point and the outer bearing recess and/or the cage track as references. Reference datums may also be created on at least one of the said housing and stub shaft during the machining process for use later in locating the bell axis.

The method of the present invention may also be used to form a cross groove CV joint in place of a Rzeppa CV joint.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

An illustrative embodiment of a CV joint10constructed and assembled in accordance with the present invention is shown inFIG. 8. As further illustrated inFIG. 7, the CV joint10generally includes a disc shaped outer bearing race40, an inner bearing race50, and a stub shaft30. The CV joint10is constructed by forming a bell shaped outer bearing race20(FIGS. 1 and 2), machining the bell shaped outer bearing race and separating the bell shaped outer bearing race20to create both the stub shaft30and the disc shaped outer bearing race40. By forming the stub shaft30and disc shaped outer bearing race40from the bell shaped outer bearing race20, a balanced CV joint10having reduced noise, vibration, and harshness issues may be easily constructed and assembled without many of the problems associated with manufacturing typical disc shaped CV joints. Forming the stub shaft30and disc shaped outer bearing race40from the bell shaped outer bearing race20also facilitates machining of each component in an accurate and precise manner. Further by forming the disc shaped outer bearing race integrally connected to the stub shaft allows the disc shaped outer bearing race40to be near net forged, thereby limiting the amount of machining necessary. In some embodiments, the near net forged surfaces of the disc shaped outer bearing race40may be formed within 0.20 mm of the final desired surface.

The bell shaped outer bearing race20is formed (Step102) in a generally conventional manner such as by forging. The bell shaped outer bearing race20includes a housing21defining a cavity19, a crown23, and a bell shaft24extending from the crown (FIG. 2). The housing21includes an outer bell surface22, outer bearing recesses48, cage tracks49and an outer bell face28. The bell shaped outer bearing race20may even be a conventionally made bell shaped outer bearing race used in a bell shaped CV joint, as shown inFIG. 1. The bell shaped outer bearing race20includes a bell axis25and at least one reference point26. In the illustrated embodiment reference points are located on the crown23within the cavity19and on the end of the bell shaft24(FIGS. 2 and 5). The reference points26are used to help position the bell shaped outer bearing race20during machining. Even though the bell shaped outer bearing race20is referred to in this application and illustrated as being bell shaped, it should be readily recognizable that the bell shaped outer bearing race does not have to be completely bell shaped. For example, the bell shaped outer bearing race20may be formed as a stub shaft30integrally connected to the outer bearing race40to minimize the amount of machining before the stub shaft and outer bearing race are separated. In the illustrated embodiment, the outer bearing recesses48and cage tracks49are near net forged to reduce machining. The bell shaped outer bearing race may be near net formed by using a collapsible punch as is well known in the art.

Next, the bell shaped outer bearing race20is machined using at least one of the reference points26to create an integrally connected stub shaft30and outer bearing race40(Step104). To machine the outer surface22about the bell axis, at least one outer ball recess48or cage track may be used in conjunction with at least one reference point26to locate the bell axis25. In the illustrated embodiment, a three prong chuck engages the outer bearing recesses48and at lest one reference point26during machining. During the machining process or after heat treating, the outer bearing recesses48may be further machined and polished to their final shape, and the first face42of the outer bearing race40may be created by machining the outer bell face28. The second face44of the outer bearing race40is also partially created during the machining process of the outer bell surface22and further created as the stub shaft30is separated from the outer bearing race40as described below. Splines32, snap ring grooves34, and a boot clip groove36may also be machined while the stub shaft30is connected to the disc shaped outer bearing race40. The majority of machining is generally done to the outer bell surface22to remove excess material in order to create the stub shaft30, specifically the stub shaft hub38integrally connected to the outer disc bearing race40. Performing the machining process while the stub shaft30is connected to the disc shaped outer bearing race40ensures that, when separated, the stub shaft axis31is in alignment with the outer bearing race axis41. Because both the stub shaft30and disc shaped outer bearing race40are machined while connected, using the reference points26for locating the bell axis25, they are balanced about aligned axes. Using the outer bearing recesses44or cage tracks49with at least one reference point allow the outer surface22to be machined to create reference datums used in the machining of the outer bearing recesses48or other operations. The reference datums may be the machined outer surface22shown inFIG. 3. By forming a bell shaped outer bearing race20such as by forming and then machining, a substantial amount of machining may be eliminated, thereby reducing costs associated with the manufacturing process, due to the ability to near net forge portions of the bell shaped outer bearing race20.

The machined bell shaped outer bearing race20is then separated into the stub shaft30and the disc shaped outer bearing race40(Step106). During separation, the second face44of the disc shaped outer bearing race40may be created (FIG. 6). Minor machining operations may be further performed to the disc shaped outer bearing race40and stub shaft30once they are separated. As stated above, by forming the bell shaped outer bearing race20, machining the bell shaped outer bearing race to create the stub shaft30and outer bearing race40as one integral piece, and then separating the stub shaft30from the disc shaped outer bearing race40creates a CV joint where the stub shaft and disc shaped outer bearing race have concentric axes when assembled into the CV joint10. Therefore, when the CV joint10is assembled the stub shaft30and disc shaped outer bearing race40are balanced about the same axis and each part is efficiently machined. Further, machining and separating using the reference points26as reference to the axis eliminates problems associated with locating the axis of the disc shaped outer bearing race40as typically encountered during the machining of disc type CV joints. The disc shaped outer bearing race40may further include passages46added before or after the outer bearing race40is separated from the stub shaft30(FIG. 5). These passages46may receive fasteners used to assemble the CV joint10.

The CV joint10is then assembled (Step108) as shown inFIGS. 5 and 6. The CV joint10further includes an inner bearing race50having a splined hub52to receive the splined portion of the stub shaft30(FIG. 7). The inner bearing recesses56on the inner bearing race50are aligned with the outer bearing recesses48on the disc shaped outer bearing race40with a ball cage60containing ball bearings62therebetween. The ball cage60may engage the cage tracks49as is well known in the art. Snap clips14may be used to couple the stub shaft30to the inner and outer bearing races40,50. A can cover80and boot can82surround the inner and outer bearing races40,50to protect them from dirt and contamination. The can cover80and boot can82may be secured to the outer bearing race40using the fasteners86as shown inFIG. 8. The boot12may be added and secured by the boot clips16to the boot can82. Generally, once the stub shaft30is separated from the disc shaped outer bearing race40, the CV joint10is assembled as is well known in the art for a typical disc CV joint.

Forming the disc shaped outer bearing race40and stub shaft30as a single integral piece allows for easier machining and a better balanced CV joint. Manufacturing costs are also reduced by eliminating complicated processes to determine the axis of the disc shaped outer bearing race40for machining. Reference datums may also be easily created for additional machining operations. As stated above, a typical bell shaped outer bearing race may be used as the bell shaped outer bearing race20. The bell shaped outer bearing race20may also be formed by forging a shape close to the integrally connected outer bearing race and stub shaft. The bell shaped outer bearing race20is then machined and separated to provide the resulting stub shaft30and outer bearing race40. The bell shaped outer bearing race20may also be near net formed to minimize the amount of machining in forming the outer disc bearing race40.

The method of the present invention may also be used to form a cross groove CV joint in place of a Rzeppa CV joint.

The foregoing discussion discloses and describes an exemplary embodiment of the present invention. One skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims that various changes, modifications and variations can be made therein without departing from the true spirit and fair scope of the invention as defined by the following claims.