Abstract:
A method of manufacturing a splined member avoids the generation of waste material and minimizes the amount of dimensional inaccuracies. A hollow cylindrical workpiece is initially provided from a material having a relatively high elongation characteristic. The material used to form the workpiece may be AA-5 154 grade aluminum alloy having an elongation characteristic that is in the range of from about 20% to about 30%, preferably in the range of from about 22% to about 28%, and most preferably about 25%. A mandrel having a plurality of external splines is inserted within workpiece, and the workpiece is deformed into engagement with the mandrel to form a splined member using a swaging process, such a rotary swaging or feed swaging. The splined member is thus formed having a plurality of internal splines and a cylindrical outer surface. The use of the swaging process avoids the generation of waste material. Also, dimensional accuracy is improved because the splined member is shaped in accordance with the precisely formed mandrel, which eliminates dimensional variations that can result from known machining practices.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of U.S. Provisional Application No. 60/608,021, filed Sep. 8, 2004, the disclosure of which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     This invention relates in general to methods of manufacturing splined members, such as are commonly used in the driveshaft assemblies. In particular, this invention relates to an improved method of manufacturing a splined member for use in such a driveshaft assembly.  
         [0003]     Drive train systems are widely used for generating power from a source and for transferring such power from the source to a driven mechanism. Frequently, the source generates rotational power, and such rotational power is transferred from the source to a rotatably driven mechanism. For example, in most land vehicles in use today, an engine/transmission assembly generates rotational power, and such rotational power is transferred from an output shaft of the engine/transmission assembly through a driveshaft assembly to an input shaft of an axle assembly so as to rotatably drive the wheels of the vehicle. To accomplish this, a typical driveshaft assembly includes a hollow cylindrical driveshaft tube having a pair of end fittings, such as a pair of tube yokes, secured to the front and rear ends thereof. The front end fitting forms a portion of a front universal joint that connects the output shaft of the engine/transmission assembly to the front end of the driveshaft tube. Similarly, the rear end fitting forms a portion of a rear universal joint that connects the rear end of the driveshaft tube to the input shaft of the axle assembly. The front and rear universal joints provide a rotational driving connection from the output shaft of the engine/transmission assembly through the driveshaft tube to the input shaft of the axle assembly, while accommodating a limited amount of angular misalignment between the rotational axes of these three shafts.  
         [0004]     Not only must a typical drive train system accommodate a limited amount of angular misalignment between the source of rotational power and the rotatably driven device, but it must also typically accommodate a limited amount of relative axial movement therebetween. For example, in most vehicles, a small amount of relative axial movement frequently occurs between the engine/transmission assembly and the axle assembly when the suspension of the vehicle articulates during normal operation, such as when the vehicle is driven over a bumpy road. To address this, it is known to provide a slip joint in the driveshaft assembly. A typical slip joint includes first and second members that have respective structures formed thereon that cooperate with one another for concurrent rotational movement, while permitting a limited amount of axial movement to occur therebetween.  
         [0005]     One type of slip joint commonly used in conventional driveshaft assemblies is a sliding spline type slip joint. A typical sliding spline type of slip joint includes male and female members having respective pluralities of splines formed thereon. The male member is generally cylindrical in shape and has a plurality of outwardly extending splines formed on the outer surface thereof. The male member may be formed integrally with or secured to an end of the driveshaft assembly described above. The female member, on the other hand, is generally hollow and cylindrical in shape and has a plurality of inwardly extending splines formed on the inner surface thereof. The female member may be formed integrally with or secured to a yoke that forms a portion of one of the universal joints described above. To assemble the slip joint, the male member is inserted within the female member such that the outwardly extending splines of the male member cooperate with the inwardly extending splines of the female member. As a result, the male and female members are connected together for concurrent rotational movement. However, the outwardly extending splines of the male member can slide relative to the inwardly extending splines of the female member to allow a limited amount of relative axial movement to occur between the engine/transmission assembly and the axle assembly of the drive train system.  
         [0006]     In the past, the male and female splined members have usually been formed from steel, and the splines of such members have been manufactured by machining portions of such members so as to provide the desired splines. Although this method has been effective, the use of the machining process to form the splines has resulted in the generation of waste material, which is inefficient. Also, the use of the conventional machining process to form the splines can generate dimensional variances that result from normal manufacturing tolerances and practices. More recently, the male and female splined members have usually been formed from aluminum alloys having relatively low elongation factors, such as 6061-T6 aluminum. The use of these aluminum alloys has been found to be desirable because aluminum is much lighter in weight than steel. However, the use of the machining process to form the splines in the aluminum members still results in the generation of waste material and dimensional inaccuracies. Thus, it would be desirable to provide an improved method of manufacturing a splined member, such as for use in a vehicular driveshaft assembly, that avoids the generation of waste material and minimizes the amount of dimensional inaccuracies.  
       SUMMARY OF THE INVENTION  
       [0007]     This invention relates to an improved method of manufacturing a splined member, such as for use in a vehicular driveshaft assembly, that avoids the generation of waste material and minimizes the amount of dimensional inaccuracies. A hollow cylindrical workpiece is initially provided from a material having a relatively high elongation characteristic. The material used to form the workpiece may be AA-5154 grade aluminum alloy having an elongation characteristic that is in the range of from about 20% to about 30%, preferably in the range of from about 22% to about 28%, and most preferably about 25%. A mandrel having a plurality of external splines is inserted within the workpiece, and the workpiece is deformed into engagement with the mandrel to form a splined member using a swaging process, such a rotary swaging or feed swaging. The splined member is thus formed having a plurality of internal splines and a cylindrical outer surface. The use of the swaging process avoids the generation of waste material. Also, dimensional accuracy is improved because the splined member is shaped in accordance with the precisely formed mandrel, which eliminates dimensional variations that can result from conventional machining practices.  
         [0008]     Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiments, when read in light of the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  is an exploded perspective view of a workpiece and a mandrel shown prior to the commencement of a first embodiment of a method of manufacturing a splined member in accordance with this invention.  
         [0010]      FIG. 2  is a perspective view similar to  FIG. 1  showing the workpiece and the mandrel disposed in a co-axially overlapping relationship.  
         [0011]      FIG. 3  is a sectional elevational view taken of the assembled workpiece and mandrel taken along line  3 - 3  of  FIG. 2 .  
         [0012]      FIG. 4  is a perspective view similar to  FIG. 2  showing the workpiece after it has been deformed about the mandrel.  
         [0013]      FIG. 5  is a sectional elevational view of the deformed workpiece and the mandrel taken along line  5 - 5  of  FIG. 4 .  
         [0014]      FIG. 6  is a sectional elevational view of the deformed workpiece after it has been removed from the mandrel.  
         [0015]      FIG. 7  is a sectional elevational view similar to  FIG. 6  showing the deformed workpiece after a machining operation has been performed thereon to form a finished splined member.  
         [0016]      FIG. 8  is an exploded perspective view showing the finished splined member, an internal seal, and an end of a driveshaft tube shown prior to assembly to form a splined driveshaft component.  
         [0017]      FIG. 9  is a sectional elevational view showing the splined member, the internal seal, and the driveshaft tube in an assembled condition to form a splined driveshaft component.  
         [0018]      FIG. 10  is an exploded perspective view showing the splined driveshaft component of  FIG. 9  and another splined driveshaft component that can be assembled to form a splined driveshaft assembly.  
         [0019]      FIG. 11  is an exploded elevational view of a workpiece and a mandrel shown prior to the commencement of a second embodiment of a method of manufacturing a splined member in accordance with this invention.  
         [0020]      FIG. 12  is an exploded elevational view of a workpiece and a mandrel shown prior to the commencement of a third embodiment of a method of manufacturing a splined member in accordance with this invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0021]     Referring now to the drawings, there is illustrated in  FIGS. 1 through 10  a first embodiment of a method of forming a splined member in accordance with this invention. The splined member may, for example, be used in a driveshaft assembly of a vehicular drive train system. However, it will be appreciated that the splined member manufactured in accordance with the method of this invention can be used in any desired environment for any desired purpose.  
         [0022]     As shown in  FIG. 1 , a workpiece, indicated generally at  10 , and a mandrel, indicated generally at  20 , are initially provided. The illustrated workpiece  10  is generally hollow and cylindrical in shape, having an outer surface  11  and an inner surface  12  that define a wall thickness that is generally uniform through the length thereof. However, the workpiece  10  may be formed having any desired shape or wall thickness.  
         [0023]     The workpiece  10  is formed from a material having a relatively high elongation characteristic. As used herein, the term “elongation characteristic” is used to designate a factor that is representative of the amount of ductility of the material used to form the workpiece  10 . The elongation factor varies directly with the amount of ductility of the material, i.e., the higher the elongation factor, the more ductile the material is, and vice versa. The elongation characteristic of the material used to form the workpiece  10  can be determined in any desired manner. For example, the elongation characteristic of the material can be determined empirically by initially providing a pair of marks at spaced apart locations on the outer surface of a piece of the material and measuring the distance therebetween. Then, the piece of the material is subjected to tensile forces, which causes it to elongate and increase the distance between the two marks. After a certain amount of such elongation has occurred, the piece of the material will fracture into two pieces. Following such fracture, the two pieces of the material are disposed adjacent to one another, and the length of the extension before the fracture occurred is measured as the distance between the two marks. By dividing the extended length between the two marks by the original length therebetween, the elongation factor can be expressed as a percentage of the original length.  
         [0024]     As used herein, the term “relatively high elongation characteristic” is used to designate an elongation characteristic that is in the range of from about 20% to about 30%, preferably in the range of from about 22% to about 28%, and most preferably about 25%. The workpiece  10  is preferably formed from an aluminum alloy material having a relatively high elongation characteristic. One example of a material that has a relatively high elongation characteristic is AA-5154 grade aluminum alloy having an H112 temper and a generally uniform wall thickness of about one-quarter inch.  
         [0025]     Alternatively, the workpiece  10  can be formed from a material having a relatively low elongation characteristic, but which is subjected to a softening process to provide it with a relatively high elongation characteristic. One well known softening process is a retrogression heat treatment process. Generally speaking, the retrogression heat treatment process is performed by rapidly heating the workpiece  10  to a sufficient temperature that provides for full or partial softening thereof, followed by relatively rapid cooling. Notwithstanding this cooling, the workpiece  10  retains the full or partial softening characteristics for at least a relatively short period of time. The deformation of the workpiece  10  is performed in the manner described below while the workpiece  10  retains the full or partial softening characteristics.  
         [0026]     The illustrated mandrel  20  is generally cylindrical in shape, including a supporting shaft portion  21  and an end portion having a plurality of axially extending external splines  22  formed on the outer surface thereof. Preferably, the external splines  22  of the mandrel  20  define an outer diameter that is smaller than an inner diameter defined by the inner surface  12  of the workpiece  10 . As a result, the mandrel  20  can be quickly and easily inserted co-axially within the workpiece  10 , as shown in  FIGS. 2 and 3 . The mandrel  20  is inserted within the workpiece  10  for deforming the workpiece  10  into a desired shape to form a splined member.  
         [0027]     Thus, the next step in the method is to deform a portion of the workpiece  10  about the axially extending external splines  22  of the mandrel  20 , as shown in  FIGS. 4 and 5 . This can be accomplished by any desired process. Preferably, however, the portion of the workpiece  10  is deformed about the axially extending external splines  22  of the mandrel  20  by a swaging process, such as by rotary swaging or feed swaging. During this swaging process, a conventional swaging tool (not shown) is moved into engagement with a portion of the outer surface  11  (see  FIGS. 1 through 3 ) of the workpiece  10 . As a result, the portion of the workpiece  10  that is engaged by the swaging tool is reduced in diameter (such as shown at  13  in  FIGS. 4 and 5 ) relative the portion of the workpiece  10  that is not engaged by the swaging tool, which remains at its original diameter (such as shown at  14  in  FIGS. 4 and 5 ). Consequently, a transition portion  15  is defined in the workpiece  10  between the reduced diameter portion  13  and the unreduced diameter portion  14 . The transition portion  15  of the workpiece  10  is preferably be frusto-conical in shape as illustrated, although such is not required.  
         [0028]     Thereafter, the mandrel  20  is removed from the workpiece  10 , as shown in  FIG. 6 , to provide a rough splined member, indicated generally at  16  in  FIG. 6 . As a result of this swaging process, the inner surface  12  of the deformed reduced diameter portion  13  of the splined member  16  is moved into engagement with the external splines  22  provided on the end portion of the mandrel  20  and re-shaped to form a plurality of internal splines  13   a  thereon, as shown in  FIG. 6 . At the same time, however, the outer surface of the deformed reduced diameter portion  13  of the splined member  16  is preferably maintained having its original generally cylindrical shape (albeit with a smaller outer diameter), as also shown in  FIG. 6 .  
         [0029]     Next, portions of the splined member  16  can be machined or otherwise re-shaped to provide a variety of desired structures thereon. For example, as shown in  FIG. 7 , one or more annular grooves  13   b  can be formed in the outer surface of the deformed reduced diameter portion  13  of the splined member  16 . The purpose for these annular grooves  13   b  will be explained below. Also, a counterbore  15   a  can be formed in the inner surface of the splined member  16  at or near the transition portion  15  thereof. The purpose for this counterbore  15   a  will also be explained below. Lastly, an annular recessed area  14   a  can be formed in the outer surface of the unreduced diameter portion  14  of the splined member  16  adjacent to an end thereof. The purpose for this annular recessed area  14   a  will also be explained below.  
         [0030]      FIGS. 8 and 9  illustrate the assembly of the splined member  16  with an internal seal  30  and an end of a driveshaft tube  40  to form a splined driveshaft component, indicated generally at  50 . Initially, the internal seal  30  (which can be a conventional elastomeric or plastic welch plug) is inserted within the splined member  16  and is press fit into the counterbore  15   a  formed on the inner surface of the transition portion  15  of the splined member  16 . Then, the end of the driveshaft tube  40  is moved co-axially about and supported on the annular recess  14   a  provided on the unreduced diameter portion  14  of the splined member  16 . Thus, the annular recess  14   a  functions as a tube seat to precisely position the driveshaft  40  relative to the splined member  16 . Preferably, the end of the driveshaft tube  40  initially engages the tube seat  14   a  of the splined member  16  in a light press fit relationship. Thereafter, the end of the driveshaft tube  40  can be permanently secured to the splined member  16  in any conventional manner, such as by welding, adhesives, and the like.  
         [0031]     As shown in  FIG. 10 , the splined driveshaft component  50  is a female splined driveshaft component that can be used with a conventional male splined driveshaft component, such as indicated generally at  60 , to form a splined driveshaft assembly. The male splined driveshaft component  60  is conventional in the art and includes a shaft portion  61  that is connected to a male splined portion having a plurality of external splines  62  provided thereon. In a manner that is well known in the art, the external splines  62  of the male splined driveshaft component  60  cooperate with the internal splines  13   a  formed on the female splined driveshaft component  50 . As a result, the male splined driveshaft component  60  and the female splined driveshaft component  50  are connected together for concurrent rotational movement. However, the external splines  62  of the male splined driveshaft component  60  can slide relative to the internal splines  13   a  of the female splined driveshaft component  50  to allow a predetermined amount of relative axial movement to occur between the male splined driveshaft component  60  and the female splined driveshaft component  50 .  
         [0032]     As discussed above, one or more annular grooves  13   b  are formed in the outer surface of the deformed reduced diameter portion  13  of the female splined driveshaft component  50 . These annular grooves  13   b  can be provided to facilitate the securement of a first end of a conventional flexible boot (not shown) about the open end of the deformed reduced diameter portion  13  of the female splined driveshaft component  50 . A second end of such a flexible boot could also be secured to the outer surface of the male splined driveshaft component  60  to prevent dirt, water, and other contaminants from entering into the region of the cooperating splines  62  and  13   a . To facilitate the securement of the second end of the flexible boot the outer surface of the male splined driveshaft component  60 , one or more similar grooves (not shown) can also be formed in the outer surface of the male splined driveshaft component  60 .  
         [0033]     Although the method of this invention has been described and illustrated in the context of the formation of a female splined member, it will be appreciated that this invention can be used to form a male splined member as well. To accomplish this, the hollow cylindrical workpiece  10  could be inserted within a hollow cylindrical mandrel (not shown) having a plurality of axially extending internal splines formed on the inner surface thereof. The hollow cylindrical workpiece  10  could then be expanded outwardly, such as by using conventional magnetic pulse forming techniques, so as to form a male splined member having a plurality of axially extending external splines formed on the outer surface thereof.  
         [0034]      FIG. 11  is an exploded elevational view of a modified workpiece, indicated generally at  10 ′, and the mandrel  20  shown prior to the commencement of a second embodiment of a method of manufacturing a splined member in accordance with this invention. In this embodiment of the method of this invention, the modified workpiece  10 ′ is generally hollow and cylindrical in shape, similar to the workpiece  10  described and illustrated above. However, the modified workpiece  10 ′ does not have a wall thickness that is generally uniform through the length thereof. Rather, the modified workpiece  10 ′ has a wall thickness that varies from a thicker portion  10   a  to a thinner portion  10   b . In this embodiment of the invention, the thicker portion  10   a  of the modified workpiece  10 ′ and the thinner portion  10   b  of the modified workpiece  10 ′ are formed from separate pieces of material that are secured together using any conventional process. For example, the thicker portion  10   a  of the modified workpiece  10 ′ and the thinner portion  10   b  of the modified workpiece  10 ′ can be secured together by a conventional friction welding process. The mandrel  20  can be inserted within the thicker portion  10   a  of the modified workpiece  10 ′ to form the internal splines  13   a  in the manner described above.  
         [0035]      FIG. 12  is an exploded elevational view of a further modified workpiece, indicated generally at  10 ″, and the mandrel  20  shown prior to the commencement of a third embodiment of a method of manufacturing a splined member in accordance with this invention. In this embodiment of the method of this invention, the further modified workpiece  10 ″ is generally hollow and cylindrical in shape, similar to the workpiece  10  described and illustrated above. However, the further modified workpiece  10 ″ does not have a wall thickness that is generally uniform through the length thereof. Rather, the further modified workpiece  10 ″ has a wall thickness that varies from a thicker portion  10   c  to a thinner portion  10   d . In this embodiment of the invention, the thicker portion  10   c  of the further modified workpiece  10 ″ and the thinner portion  10   d  of the further modified workpiece  10 ″ are formed from a single piece of material that has been formed to have relative thick and thin wall thickness portions using any conventional process. For example, the thicker portion  10   c  of the further modified workpiece  10 ″ and the thinner portion  10   d  of the further modified workpiece  10 ″ can be formed by a conventional rolling process or by a conventional butted tube extrusion process. The mandrel  20  can be inserted within the thicker portion  10   c  of the further modified workpiece  10 ″ to form the internal splines  13   a  in the manner described above.  
         [0036]     In accordance with the provisions of the patent statutes, the principle and mode of operation of this invention have been explained and illustrated in its preferred embodiments. However, it must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope.