Method of making an axle

A one-piece axle and a method of manufacture. The method may include providing a one-piece axle blank that has a shaft and a flange. The shaft may have a hole that may extend along an axis. The flange may extend radially outward from an end of the shaft. The shaft may be radially forged against a first mandrel to axially elongate the shaft.

TECHNICAL FIELD

This disclosure relates to a one-piece axle and a method of manufacture.

BACKGROUND

A multi-piece axle is disclosed in United States Patent Publication No. 2018/0022154.

SUMMARY

In at least one embodiment, a method of making an axle is provided. The method may include providing a one-piece axle blank that may have a shaft and a flange. The shaft may have a hole that may extend along an axis. The flange may extend radially outward from an end of the shaft. The shaft of the one-piece axle blank may be radially forged against a first mandrel to axially elongate the shaft.

In at least one embodiment, an axle is provided. The axle may have a shaft and a flange. The shaft may have a hole that may extend along an axis. The flange may extend radially outward from an end of the shaft. The flange may be integral with the shaft such that the axle is a one-piece component in which the flange is not a separate component that is attached to the shaft.

DETAILED DESCRIPTION

Referring toFIGS. 1 and 2, an example of a one-piece axle blank10is shown. The one-piece axle blank10may be manufactured into a one-piece axle12, which is best shown inFIGS. 9 and 10. The one-piece axle12may be provided with an axle assembly that may be part of a motor vehicle like a truck, bus, farm equipment, military transport or weaponry vehicle, or cargo loading equipment for land, air, or marine vessels. For example, the one-piece axle12may operatively connect a differential assembly to a vehicle wheel. The one-piece axle blank10and the one-piece axle12may be disposed along and may be rotatable about an axis14.

Referring toFIGS. 1-3, the one-piece axle blank10may be made of any suitable material. For example, the one-piece axle blank10may be made of a metal alloy like steel. In addition, the one-piece axle blank10may be forged from a single piece of material as will be discussed in more detail below. The one-piece axle blank10may include a shaft20and a flange22.

The shaft20may have a generally cylindrical hollow configuration and may be centered about the axis14. For instance, the shaft20may have an exterior surface30, an interior surface32, a hole34, and an end surface36.

The exterior surface30may extend continuously around the axis14and may face away from the axis14. The exterior surface30may extend from the flange22to the end surface36. As is best shown inFIG. 3, the exterior surface30may have a tapered conical configuration prior to being radially forged in which the exterior surface30becomes closer to the axis14in a direction that extends away from the flange22. As is best shown inFIG. 6, the exterior surface30may have a cylindrical or substantially cylindrical configuration after being radially forged.

The interior surface32may be disposed opposite the exterior surface30and may be spaced apart from the exterior surface30. As such, the interior surface32may face toward the axis14and may be at least partially spaced apart from the axis14. The interior surface32may extend from the end surface36toward the flange22. As is best shown inFIG. 3, the interior surface32may have a tapered conical configuration prior to being radially forged in which the interior surface32becomes closer to the axis14in a direction that extends away from the end surface36. In addition, the closed end of the interior surface32may have a substantially hemispherical shape. As is best shown inFIG. 6, the interior surface32may have multiple diameters after being radially forged. The interior surface32may at least partially define the hole34.

The hole34may extend from the end surface36toward the flange22. For example, the hole34may extend in an axial direction or a direction that extends along the axis14from the end surface36toward the flange22such that the hole34may not reach the flange22. As such, the hole34may be a blind hole that may be spaced apart from the flange22.

Referring toFIGS. 1 and 2, the end surface36may be disposed at an end of the shaft20that may be disposed opposite the flange22. The end surface36may extend from the exterior surface30to the interior surface32. In addition, the end surface36may be disposed substantially perpendicular to the axis14in one or more configurations.

The flange22may be extend from an end of the shaft20that may be disposed opposite the end surface36. Moreover, the flange22is integral with the shaft20and is not a separate component that is attached to the shaft20. The flange22may extend radially outward from the end of the shaft20or in a direction that may extend radially from or perpendicular to the axis14. In at least one configuration, the flange22may include a first side40, a second side42, an outer surface44, a ring46, and a recess48.

The first side40may be disposed opposite the end surface36. As such, the first side40may face away from the end surface36. In addition, the first side40or a portion thereof may be disposed substantially perpendicular to the axis14.

The second side42may be disposed opposite the first side. As such, the second side42may face toward the shaft20. The second side42or portion thereof may be disposed substantially perpendicular to the axis14or may be disposed parallel or substantially parallel to the first side40. The second side42may extend from the exterior surface30of the shaft20to the outer surface44.

The outer surface44may extend from the first side40to the second side42. The outer surface44may extend continuously around the axis14and may face away from the axis14. Moreover, the outer surface44may be disposed further from the axis14than the exterior surface30of the shaft20. The outer surface44may extend parallel or substantially parallel to the axis14. In at least one configuration, the outer surface44may have a variable diameter as will be discussed in more detail below.

The ring46may be provided on the first side40of the flange22. The ring46may extend radially inward from the outer surface44toward the axis14and to the recess48. As such, the ring46may be a portion of the flange22that may extend around the recess48. The ring46may have a substantially constant thickness from the first side40to the second side42. In at least one configuration, the ring46may include a plurality of lobes50.

The lobes50may protrude radially outward with respect to the axis14and the recess48. The lobes50may be provided in a repeating pattern or a repeating arrangement around the axis14. In the configuration shown, eight lobes50are provided; however, it is contemplated that a greater or lesser number of lobes50may be provided. In a configuration having an even number of lobes50, each lobe50may be disposed directly opposite another lobe50along a diametrical line that may extend through the axis14and perpendicular to the axis14. Each lobe50may have a peak52. The peak52may be a location or region of the outer surface44that is disposed furthest from the axis14. A trough54may be disposed between adjacent lobes50. The trough54may be a location or region of the outer surface44that is disposed closest to the axis14. As such, the outer surface44may have a serpentine or undulating configuration as of extends around the axis14.

As is best shown inFIGS. 1 and 2, each lobe50of the one-piece axle blank10may be free of holes. As is best shown inFIGS. 9 and 10, each lobe50of the one-piece axle12may have a lug hole56that may extend through each lobe50. Each lug hole56may receive a wheel mounting lug that may facilitate mounting of a vehicle wheel to the one-piece axle12. A lug nut may be threaded onto each wheel mounting lug to secure the wheel to the flange22of the one-piece axle12between the lug nut and the flange22.

The recess48may be disposed on the first side40of the flange22. The recess48may extend radially inward from the ring46to the axis14. In addition, the recess48may extend axially from the ring46toward the shaft20. As such, the recess48may be disposed opposite the shaft20.

Referring toFIG. 11, a flowchart of a method of making an axle is shown. Steps associated with the method are illustrated with reference toFIGS. 3-10.

At block100, the one-piece axle blank10may be forged. The one-piece axle blank10may be forged using a forging die set120, an example of which is illustrated inFIG. 3. The forging die set120may receive and forge a single piece of material into the one-piece axle blank10having the shaft20that extends from and is integrally formed with the flange22. For instance, a bar of material, such as steel, may be cut to a predetermined length that provides a sufficient volume to form the one-piece axle blank10. Although a single forging die set120is shown, it is also contemplated that multiple die sets may be employed to forge the single piece of material into the one-piece axle blank10using a sequence of forging steps.

The forging die set120may include a first die122and a second die124. The first die122and the second die124may be disposed in a first press that may actuate the first die122, the second die124, or both, along the axis14to compress and forge the single piece of material in a manner known by those skilled in the art.

The first die122may primarily form the shaft20. In at least one configuration, the first die122may have a first die cavity130that may be configured to receive the single piece of material. In the orientation shown, the first die cavity130may extend from an upper surface of the first die122that may face toward the second die124to a bottom surface that may form the end surface36. A forming shaft132may be received in the first die cavity130and may extend upward from a bottom surface of the first die122. The shaft20may be formed around the forming shaft132. As such, the forming shaft132may form the hole34in the shaft20.

The second die124may cooperate with the first die122to form the flange22. In at least one configuration, the second die124may have a second die cavity134that may face toward first die cavity130of the first die122to provide space for forging the flange22. The flange22may be formed in the second die cavity134between the first die122and the second die124.

At block102, the shaft20of the one-piece axle blank10may be radially forged or swaged to lengthen and shape the shaft20as well as to change its material thickness. Swaging or radial forging is a forming process in which a workpiece is forged or reduced to a desired size or shape by dies that exert compressive forces, such as with a succession of rapid blows from a plurality of hammers or dies that impact and act around the circumference or perimeter of the workpiece. Swaging or radial forming is typically a cold working process and is suitable for forming workpieces that have a symmetrical cross section. Swaging or radial forming may be performed using a swaging or radial forging equipment, such as a radial forging machine. Such equipment may include a gripper140, a plurality of hammers or dies142, and a first mandrel144, which are best shown inFIGS. 4 and 5. In addition, the equipment may include a second mandrel146which is best shown inFIGS. 5 and 6.

Referring toFIG. 4, the gripper140may grasp and hold the flange22. As such, the flange22may not rotate with respect to the gripper140and the flange22may not be forged by the radial forging machine, such as when the shaft20is radially forged. As such, the flange22may be completely forged before the shaft20is radially forged.

The first mandrel144may be inserted into the hole34of the shaft20. Moreover, the first mandrel144may be inserted such that the end of the first mandrel144to contact the end of the hole34. The first mandrel144may extend along the axis14and may have a cylindrical or substantially cylindrical configuration. In addition, the first mandrel144may have an outside diameter DM1that may be less than the diameter of the hole34.

Next, the dies142may impact and exert compressive forces on the exterior surface30of the shaft20. The compressive forces may be exerted in a radial direction that extends toward the axis14so that the interior surface32of the shaft20may be radially forged against the first mandrel144. The dies142may or may not rotate about an axis14with respect to the shaft20depending on the design of the swaging or radial forging machine. Similarly, the shaft20may or may not rotate about the axis14with respect to the dies142in various configurations.

The dies142may strike the exterior surface30of the shaft20simultaneously or with alternating blows. The dies142may be positioned opposite each other when an even number of dies is employed. Alternatively, dies142may be angularly offset from each other when and odd number of dies is employed.

As is best shown by comparingFIGS. 4 and 5, the compressive forces exerted by the dies142may reduce the wall thickness of the shaft20from the exterior surface30to the interior surface32. For instance, the shaft20may have a wall thickness T1at the end surface36prior to radial forging as shown inFIG. 4(and may have an increasing wall thickness in a direction that extends axially toward the flange22). After radial forging, the wall thickness may be reduced to wall thickness T2as shown inFIG. 5. As an example, the wall thickness T2may be approximately 0.354 inches (0.9 cm). In addition, radial forging may reduce the outside diameter and the inside diameter of the shaft20. For example, the shaft20may have an outside diameter DO1and an inside diameter DI1at the end surface36prior to radial forging as shown inFIG. 4. After radial forging, that radially forged portion of the shaft20may have an outside diameter DO2and an inside diameter DI2that is less than DO1and DI1, respectively, as shown inFIG. 5. As an example, the outside diameter DO2may be approximately 2.205 inches (5.6 cm) and the inside diameter DI2may be approximately 1.5 inches (3.8 cm). The inside diameter DI2may also be a diameter of the hole34after radial forging against the first mandrel144.

As is best shown by comparingFIGS. 4 and 5, the dies142may move axially with respect to the shaft20or vice versa to form the shaft20along its axial length. This relative axial movement may axially elongate the shaft20and push the end surface36away from the flange22. Moreover, the dies142may push material along the side of the dies142that faces away from the flange22, resulting in an enlarged area or bulge148between the dies142and the end surface36.

Radial forging may be paused at the position shown inFIG. 5to permit the first mandrel144to be removed from the hole34and be replaced with the second mandrel146. The second mandrel146may be inserted partially into the hole34of the shaft20, such as just through the bulge148. As such, the end of the second mandrel146may be spaced apart from the shaft20in one or more configurations. In addition, the second mandrel146may be spaced apart from the shaft20prior to resuming radial forging. The second mandrel146may extend along the axis14and may have a cylindrical or substantially cylindrical configuration.

The second mandrel146may have a smaller diameter than the first mandrel144. For instance, the second mandrel146may have an outside diameter DM2that may be less than the outside diameter DM1of the first mandrel144. As a result, the second mandrel146may allow an end portion150of the shaft20, which is best shown inFIG. 6, to be provided with a greater wall thickness than the portion of the shaft20that was radially forged using the first mandrel144. The end portion150may extend in an axial direction from the end surface36toward the flange22.

Referring toFIG. 6, radial forging may resume after the second mandrel146has been partially inserted into the hole34to radially forge the end portion150against the second mandrel146to reduce the diameter of the hole34in the end portion150from diameter DI2to diameter DI3. As such, the hole34may have a larger diameter DI2between the flange22and the end portion150than inside the end portion150. The end portion150may have a wall thickness T3that may be greater than the wall thickness T2of the portion of the shaft20that was radially forged against the first mandrel144but not radially forged against the second mandrel146. Moreover, the end portion150may be radially forged such that the shaft20may have a substantially constant outside diameter DO2between the flange22and the end surface36. The second mandrel146may then be removed from the hole34and the radially forged one-piece axle12may be released from the gripper140and removed from the radial forging machine, thereby resulting in the configuration shown inFIG. 7.

At block104, a spline160may be provided on the end portion150after the shaft20and the end portion150have been radially forged. The spline160is best shown with reference toFIGS. 8-10. Horizontal dashed lines are used inFIG. 8to illustrate differences betweenFIG. 6, in which the spline160has not been provided, andFIG. 8, in which the spline160has been provided. The spline160may be formed in any suitable manner. For instance, the spline160may be formed by roll forming the end portion150or by removing material from the exterior surface30of the end portion150to provide a plurality of spline teeth that may be arranged around the axis14. The spline teeth may extend substantially parallel to the axis14and may extend from the end surface36toward the flange22.

At block106, material removal operations may be performed. Such material removal operations are best illustrated with reference toFIG. 8, in which dashed lines are used to illustrate areas where material may be removed. Material removal operations may include removing material from the first side40of the flange22, removing material from the second side42of the flange22, removing material from the end surface36, drilling a lug hole56through each lobe50, or combinations thereof. Removing material from the end surface36may allow the shaft20of a one-piece axle12to be provided with a desired axial length or predetermined axial length. For example, the shaft20may be forged with a nominal axial length and then different amounts of material may be removed from the end surface36to provide one-piece axles12having different axial lengths. As such, a common forging process may be employed to make multiple axles having substantially the same configuration while the amount of material removed from the shaft20may vary to provide different finished axle lengths from such common forging configurations.

Removing material from the first side40of the flange22may be accomplished in any suitable manner, such as by cutting, facing, or milling the ring46, thereby providing a substantially planar surface for engagement with a vehicle wheel. Material may not be removed from the recess48.

Removing material from the second side42of the flange22may be accomplished in any suitable manner, such as by cutting, facing, or milling the second side42from the outer surface44of the flange22toward or to the exterior surface30of the shaft20, thereby providing a substantially planar surface for contacting the head of a wheel mounting lug.

The lug holes56may be drilled after removing material from the first side40and the second side42in one or more configurations.

Removing material from the end surface36may be accomplished in any suitable manner, such as by cutting, facing, or milling the end surface36to provide a desired length and a smooth surface that may facilitate coupling of the spline160with a corresponding spline on another component, such as a differential assembly. Removing material from the end surface36may be omitted in one or more configurations.

At block108, the axle or a portion thereof may be hardened. For example, a portion of the shaft20, such as the end portion150and the spline160may be induction hardened or quench hardened to increase the hardness of the spline160and optionally to harden adjacent areas of the shaft20. Moreover, it may be possible to not harden or heat treat the shaft along its entire axial length. Hardening may be performed after the spline160is provided to facilitate manufacturing and reduce cutting tool wear. In addition, hardening may be performed after removing material from the end surface36.

At block110, a plug170may be installed in the end portion150. The plug170is best shown inFIG. 9. The plug170may be installed in the hole34to seal the hole34and to prevent contaminants from entering the hole34in the shaft20. Contaminants in the hole34may otherwise lead to corrosion of the shaft20and reduced axle life. The plug170may be located adjacent to the end surface36in one or more embodiments. In addition, the plug170may extend partially through the end portion150. The plug170may be secured in any suitable manner, such as with an adhesive or other bonding technique or medium, an interference fit, or by welding. The plug170may be installed after hardening in one or more embodiments.

Providing a one-piece axle as described above may allow an axle to be made of a single piece of material, which may eliminate manufacturing and assembly steps as compared to a multi-piece axle design. For instance, assembly steps such as welding a flange to a shaft or providing fasteners or mating splines that may join a flange to a shaft may be eliminated as well as the equipment associated with performing such assembly and fabrication steps. Moreover, gaps or potential leak paths between separate axle components may be eliminated with a one-piece design, which may help improve durability and eliminate gaps or openings that may lead to corrosion or that may reduce the strength of the axle. A one-piece axle may be stronger or more durable than a multi-piece axle or solid axle shaft designs in various configurations. For example, providing a one-piece axle with a hollow shaft may provide a higher torsional section strength as compared to solid shaft designs having diameters ranging from 1.88 to 2.0 inches (47.75 to 50.8 cm). Such torsional strength may allow a single hollow shaft configuration to replace different solid axle shafts having these different diameters, which may provide improved economies of scale. A one-piece axle may also allow an axle to be made with a hole in the shaft to reduce weight of the axle, which in turn may reduce the weight of an associated axle assembly and may help improve vehicle fuel economy.