Method for securing a yoke to a tube using magnetic pulse welding techniques

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of United States Provisional Application No. 60/362,215, filed Mar. 6, 2002, the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] This invention relates in general to the use of magnetic pulse welding techniques to secure two metallic components together, such as a yoke and a driveshaft tube in a vehicular driveshaft assembly. In particular, this invention relates to an improved method for performing such a magnetic pulse welding operation that protects the inductor from potential damage that can result from the performance of this operation.

[0003] In most land vehicles in use today, a drive train system is provided for transmitting rotational power from an output shaft of an engine/transmission assembly to an input shaft of an axle assembly so as to rotatably drive one or more wheels of the vehicle. To accomplish this, a typical vehicular drive train assembly includes a hollow cylindrical driveshaft tube having first and second end fittings (such as tube yokes) secured to the opposed ends thereof. The first end fitting forms a portion of a first universal joint, which provides a rotatable driving connection from the output shaft of the engine/transmission assembly to the driveshaft tube while accommodating a limited amount of angular misalignment between the rotational axes of these two shafts. Similarly, the second end fitting forms a portion of a second universal joint, which provides a rotatable driving connection from 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 two shafts.

[0004] In vehicular driveshaft assemblies of this general type, it is usually necessary to permanently secure the first and second end fittings to the ends of the driveshaft tube. Traditionally, conventional welding techniques have been used to permanently join the first and second end fittings to the ends of the driveshaft tube. As is well known, conventional welding techniques involve the application of heat to localized areas of two metallic members, which results in a coalescence of the two metallic members. Such conventional welding techniques may or may not be performed with the application of pressure, and may or may not include the use of a filler metal. Although conventional welding techniques have functioned satisfactorily in the past, there are some drawbacks to the use thereof in joining the first and second end fittings to the ends of the driveshaft tube. First, as noted above, conventional welding techniques involve the application of heat to localized areas of the two metallic members. This application of heat can cause undesirable distortions and weaknesses to be introduced into the metallic components. Second, while conventional welding techniques are well suited for joining components that are formed from similar metallic materials, it has been found to be somewhat more difficult to adapt them for use in joining components formed from dissimilar metallic materials. Third, conventional welding techniques are not easily adapted for joining components that have different gauge thicknesses. Inasmuch as the production of vehicular driveshaft assemblies is usually a high volume process, it would be desirable to provide an improved method for permanently joining these metallic components together in a manner that avoids the drawbacks of conventional welding techniques.

[0005] Magnetic pulse welding is an alternative process that has been proposed to secure the first and second end fittings to the opposed ends of the driveshaft tube. To accomplish this, a hollow driveshaft tube having an end portion and an end fitting having a neck portion are initially provided. The end portion of the driveshaft tube can be hollow to allow the neck portion of the end fitting to be disposed co-axially therein. Alternatively, the neck portion of the end fitting can be hollow to allow the end portion of the driveshaft tube to be disposed telescopically therein. If desired, one of the adjacent surfaces of the neck portion of the end fitting or the end portion of the driveshaft tube can be tapered at least slightly relative to the other. Regardless, an annular gap is provided between the end portion of the driveshaft tube and the neck portion of the end fitting. Then, an electrical inductor is provided concentrically about or within the co-axially overlapping portions of the driveshaft tube and the end fitting. The inductor is energized to generate a magnetic field that either collapses the outer member inwardly into engagement with the inner member or expands the inner member outwardly into engagement with the outer member. In either event, the high velocity impact of the two members, as well as the large pressure exerted thereon, cause them to become permanently joined together. When one of the adjacent surfaces is tapered, the energization of the inductor causes the two members to collide one another in an axially progressive manner from one end of the tapered surface to the other. This slanting type of collision is one of the physical conditions that is usually necessary to achieve a strong, high-quality weld in the process of magnetic pulse welding.

[0006] As mentioned above, prior to being joined together, the two components are initially spaced apart from one another such that an annular gap exists between the adjacent surfaces thereof. This gap typically filled with air. Also, the adjacent surfaces of the two components are usually covered with oxide films or other contaminants. To achieve a strong weld between the two components using magnetic pulse welding (or, for that matter, any other type of cold welding process), it is important to remove these films and contaminants from the adjacent surfaces of the two components.

[0007] When the inductor is energized to form the pulsed magnetic field, the high velocity movement between the two components rapidly closes the annular gap, causing the air that was initially present in the gap to be quickly expelled outwardly therefrom. In the area where the surfaces collide with high velocity at a tapered angle, a circular cumulative flow of air is created. Fortunately, during this expulsion of the air from the annular gap, a very effective cleaning process occurs automatically as a result of the slanting collision of the adjacent surfaces of the two components to be welded. Specifically, the circular cumulative flow of air functions to remove the oxide films and other contaminants from the adjacent surfaces of the two components functions to clean such surfaces directly before the welding process occurs, which is the best type of cleaning.

[0008] This cumulative flow of air and contaminants possesses a large amount of energy and supersonic velocity. For example, it creates a loud sound like thunder if the flow is allowed to escape to the atmosphere. If the cumulative flow is reflected from an obstacle, such as a shoulder formed on the end fitting or one or more surfaces of tooling for performing the magnetic pulse welding operation, it can be directed toward the inductor that generated the magnetic field. In this instance, the insulation and other elements of the inductor can be contaminated and otherwise adversely affected in a short number of welding cycles. For example, insulation provided on the inductor can degrade significantly fast if the air and other portions of the cumulative flow are captured inside a closed space, the volume of which decreases fast. This situation is typical when, for example, the yoke shoulder is used as a stop to facilitate pre-assembly of the parts to be welded inside the inductor. In this case, a very powerful secondary flow is created as a result of a gas breakdown at the end of the collision of the welded parts through a very narrow circular gap between the shoulder and the end of the tube. Similar to the cumulative flow, this secondary flow is circular, has high velocity, and has high temperature. Unlike the cumulative flow, which is directed axially, the secondary flow is directed radially, i.e., perpendicular to the inductor insulation. The secondary flow is highly concentrated in an axial direction and acts as a sharp circular razor. The secondary flow can literally cut the inductor insulation within several welding cycles. Obviously, this is unacceptable in a manufacturing process because breakdown of the inductor is possible.

[0009] In order to prevent this from occurring, it has been suggested to provide a nonmetallic, annular shield between the axially overlapping portions of the two components and the inductor during the magnetic pulse welding process. The high velocity secondary flow created during the magnetic pulse welding operation impinges upon the shield, thus protecting the inductor therefrom premature. However, the use of such a shield has been found to be relatively time-consuming and, therefore, relatively inefficient, particularly in the context of the high volume production process associated with the manufacture of vehicular driveshaft assemblies. Thus, it would be desirable to provide an improved method for performing a magnetic pulse welding operation that reduces or eliminates the possibility of the cumulative flow escaping, as well as the possibility of forming a secondary flow in the direction of the inductor, thereby protecting the inductor from the potential wear and damage that breakdown can result therefrom.

SUMMARY OF THE INVENTION

[0010] This invention relates to an improved method for performing a magnetic pulse welding operation to secure two metallic components together, such as a yoke and a driveshaft tube in a vehicular driveshaft assembly, that protects the inductor from potential damage that can result from the performance of this operation. The yoke includes a first portion, such as a body portion, and a second portion, such as a pair of opposed yoke arms. The end of the driveshaft tube is disposed co-axially about the body portion of the yoke. An inductor axially is positioned co-axially about the overlapping portions of the end of the driveshaft tube and the body portion of the yoke. The inductor is energized to perform a magnetic pulse welding operation to secure the end of the driveshaft tube to the body portion of the yoke without generating a significant flow of air toward the inductor. To accomplish this, the yoke can be formed having an annular shoulder, and the end of the driveshaft tube can be urged into abutment with the shoulder to define an annular space therebetween. If desired, the yoke can also include an annular step, and the end of the driveshaft tube can extend about the annular step so as to define the annular space. Alternatively, the yoke can be formed having an annular shoulder, and the end of the driveshaft tube can extend about the annular shoulder to define an annular space therebetween.

[0011] 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

[0012]FIG. 1 is an exploded perspective view of a first embodiment of an end fitting and a driveshaft tube shown prior to being assembled and secured together by means of a magnetic pulse welding operation in accordance with the method of this invention.

[0013]FIG. 2 is an enlarged sectional elevational view of the first embodiment of the end fitting and the driveshaft tube illustrated in FIG. 1 shown assembled and disposed within an inductor for performing the magnetic pulse welding operation.

[0014]FIG. 3 is a further enlarged sectional elevational view showing portions of the first embodiment of the end fitting, the driveshaft tube, and the inductor illustrated in

[0015]FIGS. 1 and 2 prior to the commencement of the magnetic pulse welding operation.

[0016]FIG. 4 is an enlarged sectional elevational view similar to FIG. 3 showing portions of the first embodiment of the end fitting, the driveshaft tube, and the inductor after the performance of a conventional magnetic pulse welding operation that results in the generation of a highly intensive gas spray that can damage the inductor.

[0017]FIG. 5 is an enlarged sectional elevational view similar to FIG. 4 showing portions of the first embodiment of the end fitting, the driveshaft tube, and the inductor after the performance of a magnetic pulse welding operation that reduces or eliminates the generation of the intensive spray of air in accordance with the method of this invention.

[0018]FIG. 6 is an enlarged sectional elevational view similar to FIG. 3 showing portions of a second embodiment of the end fitting, the driveshaft tube, and the inductor prior to the commencement of the magnetic pulse welding operation in accordance with the method of this invention.

[0019]FIG. 7 is an enlarged sectional elevational view similar to FIG. 4 showing portions of the second embodiment of the end fitting, the driveshaft tube, and the inductor illustrated in FIG. 6 after the performance of a magnetic pulse welding operation in accordance with the method of this invention.

[0020]FIG. 8 is an enlarged sectional elevational view similar to FIG. 3 showing portions of a third embodiment of the end fitting, the driveshaft tube, and the inductor prior to the commencement of the magnetic pulse welding operation in accordance with the method of this invention.

[0021]FIG. 9 is an enlarged sectional elevational view showing portions of the third embodiment of the end fitting, the driveshaft tube, and the inductor illustrated in FIG. 8 after the performance of the magnetic pulse welding operation in accordance with the method of this invention.

[0022]FIG. 10 is an enlarged sectional elevational view similar to FIG. 3 showing portions of a fourth embodiment of the end fitting, the driveshaft tube, and the inductor prior to the commencement of the magnetic pulse welding operation in accordance with this invention.

[0023]FIG. 11 is an enlarged sectional elevational view showing portions of the fourth embodiment of the end fitting, the driveshaft tube, and the inductor illustrated in FIG. 10 after the performance of the magnetic pulse welding operation in accordance with the method of this invention.

[0024]FIG. 12 is an enlarged sectional elevational view similar to FIG. 3 showing portions of a fifth embodiment of the end fitting, the driveshaft tube, and the inductor prior to the commencement of the magnetic pulse welding operation in accordance with this invention.

[0025]FIG. 13 is an enlarged sectional elevational view showing portions of the fifth embodiment of the end fitting, the driveshaft tube, and the inductor illustrated in FIG. 12 after the performance of the magnetic pulse welding operation in accordance with the method of this invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] Referring now to the drawings, there is illustrated in FIGS. 1 and 2 a portion of a vehicular driveshaft assembly <b>10</b> that includes a driveshaft tube, indicated generally at <b>20</b>, and a first embodiment of an end fitting, indicated generally at <b>30</b>. Although this invention will be described and illustrated in the context of securing an end fitting to a driveshaft tube to form a portion of a vehicular driveshaft assembly, it will be appreciated that the method of this invention can be used to secure any two metallic components together for any desired purpose or application.

[0027] The illustrated driveshaft tube <b>20</b> is generally hollow and cylindrical in shape and can be formed from any desired metallic material, such as 6061 T6 aluminum alloy, for example. Preferably, the driveshaft tube <b>20</b> has an outer surface that defines a substantially constant outer diameter and an inner surface that defines a substantially constant inner diameter. Thus, the illustrated driveshaft tube <b>20</b> has a substantially cylindrical and uniform wall thickness, although such is not required. The driveshaft tube <b>20</b> has an end portion <b>21</b> that terminates at an end surface <b>22</b>.

[0028] The illustrated end fitting <b>30</b> is a tube yoke formed from a metallic material that can be either the same as or different from the metallic material used to form the driveshaft tube <b>20</b>, such steel or an alloy of aluminum, for example. The end fitting <b>30</b> includes a body portion <b>31</b> having a pair of opposed yoke arms <b>32</b> that extend therefrom in a first axial direction. A pair of aligned openings <b>33</b> are formed through the yoke arms <b>32</b> and are adapted to receive conventional bearing cups (not shown) of a universal joint cross therein. If desired, an annular groove <b>33</b><i>a </i>(see FIG. 2) can be formed within each of the openings <b>33</b> to facilitate retention of the bearing cups therein in a known manner by means of respective snap rings (not shown). A generally hollow neck portion <b>34</b> extends axially in a second axial direction from the body portion <b>31</b>. The structure of the neck portion <b>34</b> is described in detail below. If desired, an annular groove <b>35</b> (see FIG. 2) or similar recessed area can be formed on the interior of the end fitting <b>30</b>. The purpose for this annular groove <b>35</b> is explained in detail in co-pending application Ser. No. 60/362,150, filed Mar. 6, 2002, which is also owned by the assignee of this invention. The disclosure of that application is also incorporated herein by reference.

[0029]FIG. 3 illustrates the structure of the neck portion <b>34</b> of the end fitting <b>30</b> in more detail, albeit in a somewhat exaggerated manner. As shown therein, the neck portion <b>34</b> of the end fitting <b>30</b> preferably has an outer surface including a first tapered portion <b>34</b><i>a </i>that tapers outwardly from a relatively small outer diameter adjacent to the body portion <b>31</b> to an outermost point <b>34</b><i>b</i>. The outer surface of the neck portion <b>34</b> further includes a second tapered portion <b>34</b><i>c </i>that tapers inwardly from the outermost point <b>34</b><i>b </i>to the axial end of the neck portion <b>34</b>. The outer surface of the neck portion <b>34</b> is preferably smaller in diameter than the outer diameter of the body portion <b>31</b>. As a result, an annular shoulder <b>34</b><i>d </i>is defined between the neck portion <b>34</b> and the body portion <b>31</b> of the end fitting <b>30</b>.

[0030] The outermost point <b>34</b><i>b </i>of the neck portion <b>34</b> can, if desired, define an outer diameter that is either approximately equal to or slightly smaller in diameter than the inner diameter defined by the inner surface of the end portion <b>21</b> of the driveshaft tube <b>20</b>. Thus, when the end portion <b>21</b> of the driveshaft tube <b>20</b> is disposed about the neck portion <b>34</b> of the end fitting <b>30</b> as shown in FIGS. 2 and 3, the two components are positively located relative to one another. However, the outer diameter defined by the outermost point <b>34</b><i>b </i>of the neck portion <b>34</b> can, if desired, be somewhat smaller in diameter than the inner diameter defined by the inner surface of the end portion <b>21</b> of the driveshaft tube <b>20</b>. In such instance, an external fixture (not shown) may be provided for positively positioning the end portion <b>21</b> of the driveshaft tube <b>20</b> and the neck portion <b>34</b> of the end fitting <b>30</b> relative to one another. The second tapered portion <b>34</b><i>c </i>of the outer surface of the neck portion <b>34</b> is provided to facilitate the axial installation of the end portion <b>21</b> of the driveshaft tube <b>20</b> onto the neck portion <b>34</b> of the end fitting <b>30</b> in an known manner. The hollow neck portion <b>34</b> of the end fitting <b>30</b> may have a substantially uniform wall thickness, although such is not required. This tapered outer surface of the neck portion <b>34</b><i>a </i>of the end fitting <b>30</b> has been found to provide good results during the performance of a magnetic welding process that is discussed in detail below. A more detailed explanation of the structure of the neck portion <b>34</b> of the end fitting <b>30</b> can be found in U.S. Pat. No. 5,981,921 to Yablochnikov. The disclosure of that patent is incorporated herein by reference.

[0031] Typically, the end portion <b>21</b> of the driveshaft tube <b>20</b> is installed onto the neck portion <b>34</b> of the end fitting <b>30</b> by moving it axially thereover until the end surface <b>22</b> of the driveshaft tube <b>20</b> abuts the shoulder <b>34</b><i>d </i>on the end fitting <b>30</b> as shown in FIGS. 2 and 3, although such is not required. When the driveshaft tube <b>20</b> and the end fitting <b>30</b> are assembled in this manner, an annular gap or space <b>36</b> (see FIG. 3) is defined between the inner surface of the end portion <b>21</b> of the driveshaft tube <b>20</b> and outer surface of the neck portion <b>34</b> of the end fitting <b>30</b>. The size of the gap <b>36</b> can vary in radial dimension with the tapered shape of the outer surface of the neck portion <b>34</b> of the end fitting <b>30</b>, although such is not required. Typically, the radial dimension of such gap <b>36</b> will be up to a maximum of about five millimeters, although the gap <b>36</b> may have any desired dimension. Preferably, the gap <b>36</b> is substantially uniform circumferentially about the axially overlapping portions of the end portion <b>21</b> of the driveshaft tube <b>20</b> and the neck portion <b>34</b> of the end fitting <b>30</b>, although such is not required.

[0032]FIG. 2 also illustrates an inductor <b>40</b> disposed about the assembly of the driveshaft tube <b>20</b> and the first embodiment of the end fitting <b>30</b> prior to the performance of a magnetic pulse welding operation for securing the two components together in accordance with the method of this invention. The inductor <b>40</b> can be formed having any desired structure, such as that shown and described in U.S. Pat. No. 4,129,846 to Yablochnikov. The disclosure of that patent is incorporated herein by reference. The inductor <b>40</b> is connected to a schematically illustrated control circuit for selectively operating same. As shown in FIG. 2, a first end of the inductor <b>40</b> is connected to a first electrical conductor <b>41</b>, while a second end of the inductor <b>40</b> is connected through a discharge switch <b>42</b> to a second electrical conductor <b>43</b>. A plurality of high voltage capacitors <b>44</b> or similar energy storage devices are connected between the first and second electrical conductors <b>41</b> and <b>43</b>. The first electrical conductor <b>41</b> is also connected to a source of electrical energy <b>45</b>, while the second electrical conductor <b>43</b> is connected through a charging switch <b>46</b> to the source of electrical energy <b>45</b>. The structure and operation of the control circuit is described in detail in U.S. Pat. No. 5,981,921 to Yablochnikov, and the disclosure of that patent is also incorporated herein by reference.

[0033] The operation of the inductor <b>40</b> to perform the magnetic pulse welding operation is well known in the art, and reference is again made to the above-referenced U.S. Pat. No. 5,981,921 to Yablochnikov for a detailed explanation. Briefly, however, the inductor <b>40</b> is operated by initially opening the discharge switch <b>42</b> and closing the charging switch <b>46</b>. This allows electrical energy to be transferred from the source of electrical energy <b>45</b> to each of the capacitors <b>44</b>. When the capacitors <b>44</b> have been charged to a predetermined voltage, the charging switch <b>46</b> is opened. Thereafter, when it is desired to operate the inductor <b>40</b>, the discharge switch <b>42</b> is closed. As a result, a high energy pulse of electrical current flows from the capacitors <b>44</b> through the inductor <b>40</b>, thereby generating an immense and momentary electromagnetic field about the end portion <b>21</b> of the driveshaft tube <b>20</b>.

[0034] This electromagnetic field exerts a very large force on the outer surface of the end portion <b>21</b> of the driveshaft tube <b>20</b>, causing it to collapse inwardly at a high velocity onto the neck portion <b>34</b> of the end fitting <b>30</b>, as shown in FIG. 4. The resulting impact of the inner surface of the end portion <b>21</b> of the driveshaft tube <b>20</b> with the outer surface of the neck portion <b>34</b> of the end fitting <b>30</b> causes a weld or molecular bond to occur therebetween, such as shown at the region <b>47</b> in FIG. 4. The size and location of the weld region <b>47</b> will vary with a variety of factors, such as the size of the gap <b>36</b>, the size, shape, and nature of the metallic materials used to form the driveshaft tube <b>20</b> and the end fitting <b>30</b>, the size and shape of the inductor <b>40</b>, the angle and velocity of the impact between the end portion <b>21</b> of the driveshaft tube <b>20</b> and the neck portion <b>34</b> of the end fitting <b>30</b>, and the like. It will be appreciated that the illustrated weld region <b>47</b> is intended to be representative of an exemplary prime welding area that provides the best possible adherence of the driveshaft tube <b>20</b> to the end fitting <b>30</b>, and that other areas of the driveshaft tube <b>20</b> and the end fitting <b>30</b> may also be welded together as well during this process.

[0035] Prior to the energization of the inductor <b>40</b> to perform a magnetic pulse welding operation, the annular gap <b>36</b> between the inner surface of the driveshaft tube <b>20</b> and the outer surface of the end fitting <b>30</b> is typically filled with air. Also, the adjacent inner surface of the driveshaft tube <b>20</b> and the outer surface of the end fitting <b>30</b> are usually covered with oxide films or other contaminants. To achieve a strong weld between these two components using magnetic pulse welding (or, for that matter, any other type of cold welding process), it is important to remove these films and contaminants from the adjacent surfaces. When the inductor <b>40</b> is energized to form the pulsed electromagnetic field as described above, the inner surface of the driveshaft tube <b>20</b> and the outer surface of the end fitting <b>30</b> engage one another at a relatively high velocity. This high velocity relative movement rapidly closes the annular gap <b>36</b>, causing the air and the rest of the cumulative flow to be captured inside a closed space, the volume of which decreases rapidly and, therefore, becomes relatively small, such as shown in FIG. 4. As a result, a high velocity, high temperature secondary flow, such as shown at <b>48</b> in FIG. 4, can be sprayed generally radially outwardly from between the driveshaft tube <b>20</b> and the end fitting <b>30</b> during the magnetic pulse welding operation. Because the inductor <b>40</b> is typically disposed in a relatively close proximity about the driveshaft tube <b>20</b> and the end fitting <b>30</b> during the magnetic pulse welding operation, this secondary flow <b>48</b> may impinge upon the inner surface of the inductor <b>40</b>. As a result, the inductor <b>40</b> can suffer premature wear and damage.

[0036] This invention contemplates several alternative methods for reducing or eliminating the occurrence of this high velocity secondary flow <b>48</b> so as to protect the inductor <b>40</b> from premature wear and damage during the performance of the magnetic pulse welding operation. FIG. 5 illustrates the driveshaft tube <b>20</b> and the first embodiment of the end fitting <b>30</b> after the inductor <b>40</b> has been energized in the manner described above to perform a magnetic pulse welding operation in accordance with the method of this invention. As shown therein, the end surface <b>22</b> of the driveshaft tube <b>20</b> has been collapsed into engagement with a portion of the shoulder <b>34</b><i>d </i>of the end fitting <b>30</b>, while the remainder of the end portion <b>21</b> of the driveshaft tube <b>20</b> has been collapsed into engagement with the outer surface of the neck portion <b>34</b> of the end fitting <b>30</b> as described above. As a result, the air that was present in the gap <b>36</b> before the commencement of the magnetic pulse welding operation and the rest of the cumulative flow are captured, either partially or completely, in an annular space <b>49</b> defined between the inner surface of the end portion <b>21</b> of the driveshaft tube <b>20</b>, the outer surface of the neck portion <b>34</b> of the end fitting <b>30</b>, and the interior portion of the shoulder <b>34</b><i>d </i>of the end fitting <b>30</b>. The air and particles of matter contained in the annular space <b>49</b> are, therefore, not rapidly expelled (or at least not as rapidly expelled) from the gap <b>36</b> during the magnetic pulse welding operation in the manner of the high velocity secondary flow <b>48</b> described above. Thus, the air and particles of matter contained in the annular space <b>49</b> will not damage the inductor <b>40</b> as previously discussed. The end surface <b>22</b> of the driveshaft tube <b>20</b> can be caused to collapse into engaged with the shoulder <b>34</b><i>d </i>of the end fitting <b>30</b> by urging the end fitting <b>30</b> axially into engagement with such shoulder <b>34</b><i>d </i>prior to and during the magnetic pulse welding operation or in any other desired manner.

[0037]FIG. 6 is an enlarged sectional elevational view similar to FIG. 3 showing a second embodiment of the end fitting, indicated generally at <b>30</b>′, that can be used in the method of this invention. The second embodiment of the end fitting <b>30</b>′ is generally similar to the first embodiment of the end fitting <b>30</b> described above, and like reference numbers are used to illustrate similar structures therein. However, the neck portion <b>34</b> of the modified end fitting <b>30</b>′ has a recess <b>50</b> formed in the outer surface thereof. In the illustrated embodiment, the recess <b>50</b> is annular in shape, extending about the entire outer surface of the neck portion <b>34</b>. However, the recess <b>50</b> need not extend about the entire outer surface of the neck portion <b>34</b>, but rather may extend about only a portion thereof. Furthermore, a plurality of individual recesses <b>50</b> may be provided on the outer surface of the neck portion <b>34</b> if desired. In the illustrated embodiment, the recess <b>50</b> is formed in the outer surface of the neck portion <b>34</b> adjacent to the shoulder <b>34</b><i>d</i>. However, the recess <b>50</b> may be formed at any desired location in the outer surface of the neck portion <b>34</b>.

[0038]FIG. 7 illustrates the driveshaft tube <b>20</b> and the modified end fitting <b>30</b>′ after the inductor <b>40</b> has been energized in the manner described above to perform a magnetic pulse welding operation in accordance with the method of this invention so as to reduce or eliminate the generation of the high velocity secondary flow <b>48</b> shown in FIG. 4. As shown therein, the end surface <b>22</b> of the driveshaft tube <b>20</b> has been collapsed into engagement with a portion of the shoulder <b>34</b><i>d </i>of the end fitting <b>30</b>′, while the remainder of the end portion <b>21</b> of the driveshaft tube <b>20</b> has been collapsed into engagement with the outer surface of the neck portion <b>34</b> as described above. As a result, the air that was present in the gap <b>36</b> before the commencement of the magnetic pulse welding operation and the rest of the cumulative flow are captured, either partially or completely, in an annular space <b>51</b> defined between the inner surface of the end portion <b>21</b> of the driveshaft tube <b>20</b>, the recess <b>50</b> formed in the outer surface of the neck portion <b>34</b> of the modified end fitting <b>30</b>′, and the shoulder <b>34</b><i>d </i>of the end fitting <b>30</b>. As previously discussed, such contained air and the rest of the cumulative flow will not be rapidly expelled (or least not as rapidly expelled) from the annular space <b>51</b> and, therefore, will not damage the inductor <b>40</b> in the manner of the high velocity secondary flow <b>48</b> described above.

[0039]FIG. 8 is an enlarged sectional elevational view similar to FIG. 3 showing a third embodiment of the end fitting, indicated generally at <b>30</b>″, that can be used in the method of this invention. The third embodiment of the end fitting <b>30</b>″ is generally similar to the first embodiment of the end fitting <b>30</b> described above, and like reference numbers are used to illustrate similar structures therein. However, the neck portion <b>34</b> of the modified end fitting <b>30</b>″ has an annular step <b>60</b> formed in the outer surface thereof. The illustrated step <b>60</b> has a generally radially outwardly facing surface <b>60</b><i>a </i>that is tapered slightly to facilitate the installation of the end portion <b>21</b> of the driveshaft tube <b>20</b> thereover and to positively position the end portion <b>21</b> of the driveshaft tube <b>20</b> on the neck portion <b>34</b> of the end fitting <b>30</b>. To accomplish this, the generally radially outwardly facing surface <b>60</b><i>a </i>can be tapered at an angle in the range of from about five degrees to about nine degrees relative to the inner circumferential surface of the end portion <b>21</b> of the driveshaft tube <b>20</b>, for example.

[0040] The illustrated step <b>60</b> also has a generally axially facing surface <b>60</b><i>b </i>that extends generally radially relative to an axis of rotation defined by the driveshaft tube <b>20</b> and the modified end fitting <b>30</b>″. In the illustrated embodiment, the step <b>60</b> is annular in shape, extending about the entire outer surface of the neck portion <b>34</b>. However, the step <b>60</b> need not extend about the entire outer surface of the neck portion <b>34</b>, but rather may extend about only a portion thereof. In the illustrated embodiment, the step <b>60</b> is formed in the outer surface of the neck portion <b>34</b> adjacent to the shoulder <b>34</b><i>d</i>. However, the step <b>60</b> may be formed at any desired location in the outer surface of the neck portion <b>34</b>.

[0041]FIG. 9 illustrates the driveshaft tube <b>20</b> and the modified end fitting <b>30</b>″ after the inductor <b>40</b> has been energized in the manner described above to perform a magnetic pulse welding operation in accordance with the method of this invention so as to reduce or eliminate the generation of the high velocity secondary flow <b>48</b> shown in FIG. 4. As shown therein, the end surface <b>22</b> of the driveshaft tube <b>20</b> has been collapsed into engagement with the step <b>60</b> of the end fitting <b>30</b>″, while the remainder of the end portion <b>21</b> of the driveshaft tube <b>20</b> has been collapsed into engagement with the outer surface of the neck portion <b>34</b> as described above. During this operation, the step <b>60</b> may be somewhat deformed, as shown in FIG. 9. As a result, the air that was present in the gap <b>36</b> before the commencement of the magnetic pulse welding operation and the rest of the cumulative flow are captured, either partially or completely, in an annular space <b>61</b> defined between the inner surface of the end portion <b>21</b> of the driveshaft tube <b>20</b>, the step <b>60</b>, and the outer surface of the neck portion <b>34</b> of the modified end fitting <b>30</b>″. As previously discussed, such contained air and the rest of the cumulative flow will not be rapidly expelled from the annular space <b>61</b> and, therefore, will not damage to the inductor <b>40</b> in the manner of the high velocity secondary flow <b>48</b> described above.

[0042] The provision of the step <b>60</b> on the third embodiment of the end fitting <b>30</b>″ will typically provide for better containment of the air and the rest of the cumulative flow that were present in the gap <b>36</b> before the commencement of the magnetic pulse welding operation than the first and second embodiments of the end fitting <b>30</b> and <b>30</b>′ described above. However, because the end portion <b>21</b> of the driveshaft tube <b>20</b> initially abuts the radially outwardly facing surface <b>60</b><i>a </i>of the step <b>60</b> on the third embodiment of the end fitting <b>30</b>″ during the magnetic pulse welding operation (instead of being free to move radially inwardly as with the first and second embodiments of the end fitting <b>30</b> and <b>30</b>′ described above), it will be appreciated that the provision of this step <b>60</b> may require the use of additional electrical energy to insure that the interior portion of the inner surface of the driveshaft tube <b>20</b> abuts the outer surface of the modified end fitting <b>30</b>″ at a sufficient velocity as to complete the magnetic pulse welding operation.

[0043] To minimize the amount of additional electrical energy to perform the magnetic pulse welding operation, a groove (shown in phantom at <b>62</b> in FIGS. 8 and 9) can be formed in the step <b>60</b> on the third embodiment of the end fitting <b>30</b>″. The groove <b>62</b> can extend continuously about the circumference of the end fitting <b>30</b>″ or only partially thereabout. Furthermore, the groove <b>62</b> can be embodied as a plurality of discontinuous recesses formed about the circumference of the end fitting <b>30</b>″. The purpose of the groove <b>62</b> is to mechanically weaken the step <b>60</b>, thereby allowing the step <b>60</b> to be more easily deformed when the magnetic pulse welding operation is performed. Such deformation will minimize the amount of additional electrical energy to perform the magnetic pulse welding operation, while still providing the step <b>60</b> for better containment of the air and cumulative flow in the annular space <b>61</b>.

[0044]FIG. 10 is an enlarged sectional elevational view similar to FIG. 3 showing a fourth embodiment of the end fitting, indicated generally at <b>30</b>′″, that can be used in the method of this invention. The fourth embodiment of the end fitting <b>30</b>′″ is generally similar to the first embodiment of the end fitting <b>30</b> described above, and like reference numbers are used to illustrate similar structures therein. However, the neck portion <b>34</b> of the modified end fitting <b>30</b>′″ has a modified step <b>70</b> formed in the outer surface thereof. The modified step <b>70</b> has a generally radially outwardly facing surface <b>70</b><i>a </i>that is tapered slightly to facilitate the installation of the end portion <b>21</b> of the driveshaft tube <b>20</b> thereover, similar to the generally radially outwardly facing surface <b>60</b><i>a </i>described above. The modified step <b>70</b> also has a generally axially facing surface <b>70</b><i>b </i>that is angled somewhat concavely relative to an axis of rotation defined by the driveshaft tube <b>20</b> and the end fitting <b>30</b>′″. For example, the generally axially facing surface <b>70</b><i>b </i>can be tapered at an angle in the range of from about thirty degrees to about sixty degrees relative to the axis of rotation defined by the driveshaft tube <b>20</b> and the modified end fitting <b>30</b>′″. In the illustrated embodiment, the modified step <b>70</b> is annular in shape, extending about the entire outer surface of the neck portion <b>34</b> of the modified end fitting <b>30</b>′″. However, the modified step <b>70</b> need not extend about the entire outer surface of the neck portion <b>34</b>, but rather may extend about only a portion thereof.

[0045]FIG. 11 illustrates the driveshaft tube <b>20</b> and the modified end fitting <b>30</b>′″ after the inductor <b>40</b> has been energized in the manner described above to perform a magnetic pulse welding operation in accordance with the method of this invention so as to reduce or eliminate the generation of the high velocity secondary flow <b>48</b>. As shown therein, the end surface <b>22</b> of the driveshaft tube <b>20</b> has been collapsed into engagement with the modified step <b>70</b> of the end fitting <b>30</b>′″, while the remainder of the end portion <b>21</b> of the driveshaft tube <b>20</b> has been collapsed into engagement with the outer surface of the neck portion <b>34</b> as described above. During this operation, the modified step <b>70</b> may be somewhat deformed, as shown in FIG. 11. As a result, the air that was present in the gap <b>36</b> before the commencement of the magnetic pulse welding operation and the rest of the cumulative flow are captured, either partially or completely, in an annular space <b>71</b> defined between the inner surface of the end portion <b>21</b> of the driveshaft tube <b>20</b>, the modified step <b>70</b>, and the outer surface of the neck portion <b>34</b> of the modified end fitting <b>30</b>′″. As previously discussed, such contained air and cumulative flow will not be rapidly expelled from the annular space <b>71</b> and, therefore, will not damage the inductor <b>40</b> in the manner of the high velocity secondary flow <b>48</b> described above.

[0046] Because of the concave shape of the modified step <b>70</b>, the provision of a groove in the modified step <b>70</b> (such as the groove <b>62</b> in the step <b>60</b> described above and shown in FIGS. 8 and 9) may not be necessary or desirable. However, such a groove may be provided in the modified step <b>70</b> if desired.

[0047]FIG. 12 is an enlarged sectional elevational view similar to FIG. 3 showing a fifth embodiment of the end fitting, indicated generally at <b>30</b>″″, that can be used in the method of this invention. The fifth embodiment of the end fitting <b>30</b>″″ is generally similar to the first embodiment of the end fitting <b>30</b> described above, and like reference numbers are used to illustrate similar structures therein. In this embodiment, however, the end portion <b>21</b> of the driveshaft tube <b>20</b> does not abut the annular shoulder <b>34</b><i>d </i>that is defined between the neck portion <b>34</b> and the body portion <b>31</b> of the end fitting <b>30</b>, but rather extends axially beyond such annular shoulder <b>34</b><i>d</i>. To facilitate this, the outer surface of the driveshaft tube <b>20</b> may have a generally radially outwardly facing surface <b>80</b> that is tapered slightly to facilitate the installation of the end portion <b>21</b> of the driveshaft tube <b>20</b> thereover. The generally radially outwardly facing surface <b>80</b> can be tapered at an angle in the range of from about five degrees to about nine degrees relative to the inner circumferential surface of the end portion <b>21</b> of the driveshaft tube <b>20</b>, for example.

[0048]FIG. 13 illustrates the driveshaft tube <b>20</b> and the modified end fitting <b>30</b>″″ after the inductor <b>40</b> has been energized in the manner described above to perform a magnetic pulse welding operation in accordance with the method of this invention so as to reduce or eliminate the generation of the high velocity secondary flow <b>48</b> shown in FIG. 4. As shown therein, the end portion <b>21</b> of the driveshaft tube <b>20</b> has been collapsed into engagement with the tapered outer surface <b>34</b><i>a </i>of the neck portion <b>34</b> as described above. During this operation, the annular shoulder <b>34</b><i>d </i>may be somewhat deformed, as shown in FIG. 13. As a result, the air that was present in the gap <b>36</b> before the commencement of the magnetic pulse welding operation and the rest of the cumulative flow are captured, either partially or completely, in an annular space <b>81</b> defined between the inner surface of the end portion <b>21</b> of the driveshaft tube <b>20</b>, the annular shoulder <b>34</b><i>d</i>, and the outer surface of the neck portion <b>34</b> of the modified end fitting <b>30</b>″″. As previously discussed, such contained air and the rest of the cumulative flow will not be rapidly expelled from the annular space <b>81</b> and, therefore, will not damage to the inductor <b>40</b> in the manner of the high velocity secondary flow <b>48</b> described above.

[0049] 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 embodiment. 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.