CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. provisional application Serial No.

62/744,328 filed October 11, 2018, the entire disclosure of which is hereby incorporated by reference.

TECHNICAL FIELD

[0002] This invention relates to a vehicle drivetrain assembly for use in transmitting torque between a vehicle engine and driving wheels, and the invention also relates to a method for making the vehicle drivetrain assembly.

BACKGROUND ART

[0003] Drivetrain assemblies for vehicles are used to transmit torque between a power plant and driving wheels of a vehicle upon rotation about a central axis during the vehicle driving.

SUMMARY OF THE INVENTION

[0004] The present invention provides a vehicle drivetrain assembly constructed of first and second torque transmitting members, one of which is aluminum and the other of which is steel, that are joined by an electromagnetic pulse weld progressively applied along a radial direction relative to the central axis of the assembly so as to provide a lightweight construction.

[0005] A disclosed vehicle drivetrain assembly constructed according to the invention includes a first torque transmitting member made of aluminum and has a planar plate portion with a round opening through which a central axis of the assembly extends. The vehicle drivetrain assembly also includes a second torque transmitting member that is made of steel and has an annular connection location that feces axially relative to the central axis and extends around the round opening of the planar plate portion of the first aluminum member. An electromagnetic pulse weld of the vehicle drivetrain assembly forms and connects the plate portion of the first aluminum member around its round opening with die connection location of the second steel member.

[0006] As disclosed, the first aluminum member is a clutch hub or housing having an axially extending thin-walled spline portion, and the second steel member is a sun gear, a ring gear, a torque transmitting hub or a shaft.

[0007] As also disclosed by another embodiment of the vehicle drivetrain assembly, the electromagnetic pulse weld includes aluminum of a four digit grade whose first digit is lower than the first number of the four digit grade of aluminum of the first aluminum member remote from the weld.

[0008] A disclosed method for making a vehicle drivetrain assembly according to the invention is performed by: positioning a planar plate portion of a first aluminum torque transmitting member having a round opening with a central axis in a spaced relationship adjacent an annular connection location of a second steel torque transmitting member with the connection location facing axially relative to the central axis and extending around the opening of the first aluminum member, and applying an electromagnetic pulse weld that forms and welds the plate portion of the first aluminum member to the connection location of the second steel member.

[0009] As disclosed, the method uses a first aluminum member that is a clutch hub or housing having an axially extending thin-walled spline portion, and uses a second steel member that is a sun gear, a ring gear, a torque transmitting hub or a shaft.

[0010] As also disclosed by another practice of the method for making the vehicle drivetrain assembly, prior to performing the electromagnetic pulse welding, a third member is positioned between the first aluminum member and the second steel member and is made of aluminum of a lower grade than the first aluminum member. The third aluminum member has a thickness less than 3 mm. and as disclosed a thickness of 1.5 mm. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIGURE 1 is a sectional view without most of its background for illustrating a vehicle drivetrain assembly having connected aluminum and steel members that are eiectromagnetically pulse welded to each other.

[0012] FIGURE 1a is an enlarged view of a portion of Figure 1 illustrating a portion of the vehicle drivetrain assembly where the aluminum member is formed and eiectromagnetically pulse welded to the steel member.

[0013] FIGURE 1b is a partial sectional view taken along the direction of line 1b- 1b of

Figure 1 to illustrate a thin-walled spline portion of the aluminum member.

[0014] FIGURE 2 is a sectional view of the vehicle drivetrain assembly taken as in Figure 1 but before the electromagnetic pulse welding.

[0015] FIGURE 2a is an enlarged view of a portion of Figure 2 similar to Figure 1a but before the forming and electromagnetic pulse welding.

[0016] FIGURE 3 is a view of another embodiment of the vehicle drivetrain assembly taken in the same sectional manner as Figure 1 but also having another aluminum member that is of a lower grade than the first aluminum member and that is located at the electromagnetic pulse weld for enhancing the weld strength.

[0017] FIGURE 3a is an enlarged view of a portion of Figure 3 similar to Figure 1a and illustrating the additional aluminum member that is at the formed electromagnetic pulse weld.

[0018] FIGURE 4 is a view of the alternate embodiment of the vehicle drivetrain assembly shown in Figure 3 and is similar to Figure 2 before the forming and electromagnetic pulse welding shown in Figures 3 and 3a.

[0019] FIGURE 4a is an enlarged view of a portion of Figure 4 showing the vehicle drivetrain assembly components prior to the forming and electromagnetic pulse welding. [0020] FIGURE 5 is a view that illustrates the manner in which the embodiment of Figures 1 and 2 has its aluminum member elecfromagnetically pulse welded in a progressive manner along a radial direction with respect to the central axis of the vehicle drivetrain assembly to form the weld.

[0021] FIGURE 6 is a view similar to Figure 5 that shows the manner in which the two aluminum members of the embodiment of Figures 3 and 4 are progressively formed by the electromagnetic pulse welding along a radial direction with respect to the central axis of the vehicle drivetrain assembly to form the weld.

[0022] FIGURE 7 is a greatly enlarged view that illustrates the atomic bonding of the aluminum and steel members to each other.

[0023] FIGURE 8 is a flow chart illustrating the manner in which the one embodiment of the vehicle drivetrain assembly shown in Figures 1, 1 a, 2, 2a and 5 is processed.

[0024] FIGURE 9 is another flow chart illustrating the manner in which the other vehicle drivetrain assembly shown in Figures 3, 3a, 4, 4a and 6 is processed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] With reference to Figure 1, a vehicle drivetrain assembly generally indicated by 10 is constructed in accordance with the invention by the method of the invention and includes a first torque transmitting member 12 made of aluminum, a second torque transmitting member 14 made of steel and an electromagnetic pulse weld 16 that connects the members to each other as is hereinafter more fully described. Both the construction of the vehicle drivetrain assembly 10 and the method of making the assembly will be described in an integrated manner to facilitate an understanding of different aspects of the invention.

[0026] With continuing reference to Figure 1, the aluminum member 12 includes a planar plate portion 18 of a round shape having a central round opening 20 through which a rotational central axis A of the assembly extends. The second steel member 14 includes an annular connection location 22 that faces axially relative to the central axis A as best shown in Figure 2b and that extends around the round opening 20 of the planar plate portion 18 of the aluminum member 12. The electromagnetic pulse weld 16 as shown in Figure 1b forms and connects the plate portion 18 of the first aluminum member 12 around its round opening 20 with the connection location 22 of the second steel member 14. Thus, the second steel member 14 has durability for use as required while the first aluminum member 12 advantageously provides the vehicle drivetrain assembly with a lighter construction than would be the case with making it of steel.

[0027] As illustrated in Figures 1 and 2, the first aluminum member 12 is a clutch hub or housing defining die plate portion 18 and also having an axially extending thin-walled spline portion 24 which includes thin-walled splines 26 shown in Figure 1b.

[0028] As also shown in Figures 1 and 2, die second steel member 14 is shown as a sun gear having helical teeth 28 and also can be constructed as a ring gear, torque transmitting hub or a shaft.

[0029] As illustrated in Figure 5, the electromagnetic pulse welding forms the plate portion

18 of the aluminum member 12 progressively in a radial direction with respect to the central axis of the assembly as illustrated by the schematic arrows 30 to form the weld 16 to the steel member 14. The electromagnetic pulse welding provides the weld 16 as illustrated in the greatly magnified (1000x) view of Figure 7 at an atomic level so as to secure the aluminum and steel to each other.

[0030] As illustrated in Figure 8, the flow chart 32 illustrates in step 34 the positioning of the aluminum and steel members adjacent to each other as also shown in Figure 2 and in step 36 shows applying the electromagnetic pulse weld that forms the atomic bonding of the aluminum and steel.

[0031] With reference to Figures 3, 3a, 4 and 4a, another embodiment of the vehicle drivetrain assembly is indicated generally by 10' and has the same construction as the previously described embodiment except as will be discussed. As such, like reference numerals are applied to the like components thereof and much of the previous description is applicable such that no repetition thereof is necessary and thus will not be repeated. However, in embodiment 10', another aluminum member 38 is initially positioned as shown in Figure 4a between the connection location 22 of the steel member 14 and the plate portion 18 of the aluminum member 12 in preparation for the electromagnetic pulse welding. This aluminum member 38 is of a lower grade aluminum than the first aluminum member 12 and thus enhances the atomic bonding to the steel member 14. More specifically the aluminum member 38 is of a grade with a four digit member whose first digit is lower than the first digit of the four digit member of the grade of the first aluminum member 12 so as to form easier due to its less strength resulting from less alloying. Further, the aluminum member 38 extends around the opening 20 of the plate portion 18 of aluminum member 12 positioned adjacent the steel member connection location 22 where the electromagnetic pulse welding provides the atomic bonding. Also, the aluminum member 38 has a thickness less than 3 mm., preferably 1.5 mm. which herein means 1.5 mm. with a tolerance of plus or minus 10%, so the relatively thin aluminum has less mass than a thicker aluminum member. Thus, the aluminum member 18 is accelerated faster and has a greater impact for providing the better atomic bonding with the steel as is also provided by its less alloyed lower grade. The thicker first aluminum member 12 also atomically bonds with the lower grade aluminum of the thin aluminum member 38.

[0032] As illustrated in Figure 6, the electromagnetic pulse welding forms both the plate portion 18 of the aluminum member 12 and the aluminum member 38 progressively in a radial direction with respect to the central axis of the assembly as illustrated by the schematic arrows 30 to form the weld 16 with the steel member 14.

[0033] As illustrated in Figure 9, the flow chart 32' illustrates in step 34' the positioning of the aluminum members 12 and 38 and the and steel member 14 adjacent to each other as also shown in Figure 3 and in the step 36 shows the next step of applying the electromagnetic pulse weld that forms the atomic bonding of the aluminum and steel.

[0034] While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.