WO2016133871A1

WO2016133871A1 - Zinc metallized corrosion barrier for a driveshaft

Info

Publication number: WO2016133871A1
Application number: PCT/US2016/018014
Authority: WO
Inventors: Gregory A. FETT; Thomas M. O'neil
Original assignee: Dana Automotive Systems Group LLC
Current assignee: Dana Automotive Systems Group LLC
Priority date: 2015-02-18
Filing date: 2016-02-16
Publication date: 2016-08-25
Anticipated expiration: 2017-08-18

Abstract

A method for protecting joined components from salt or other environmental hazards is described. The method may include joining an end fitting into a driveshaft tube which results in a gap between the two. The gap may be cleaned and dried before a moisture protecting liquidized metal coating is applied. The coating may be sprayed on as the joined end fitting and tube are rotated together. The coating fills the gap and extends laterally beyond the gap and may be subsequently covered with a phenolic resin.

Description

TITLE

ZINC METALIZED CORROSION BARRIER FOR A DRIVESHAFT

RELATED APPLICATION

This application claims priority to and benefit from U.S. Patent

Application Serial No. 62/117,593 filed on February 18, 2015 which is currently pending and fully incorporated by reference herein.

FIELD OF THE INVENTION

A method for preventing corrosion between two components on a driveshaft assembly. More specifically, the method relates to preventing corrosion between two components of a driveshaft made of different materials.

BACKGROUND OF THE INVENTION

The magnetic pulse welding technique is known and commonly used as a way to join two components together. Driveshaft assemblies, comprising a driveshaft tube and an end fitting, can be formed using this technique. US RE 41 ,101 to Yablochnikov is one example of the technique and is incorporated by reference herein.

In brief summary, the technique comprises providing a hollow driveshaft tube with an end opening, where the end opening is initially disposed coaxially around a neck portion of an end fitting, is provided. Before the magnetic pulse welding operation occurs, an annular gap exists between the driveshaft tube and the end fitting. Then, an electrical inductor is provided concentrically about or within the coaxially overlapping portions of the driveshaft tube and the end fitting. The inductor is energized to generate a magnetic field that either collapses the outer component (in this case the driveshaft tube end) inwardly into engagement with the inner component or expands the inner component (in this case the neck of the end fitting) into engagement with the outer

component. In either event, the high velocity impact of the two components, 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 components to collide into 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.

A gap will remain at the interface between the end surface of the drive shaft tube and the shoulder on the end fitting after magnetic pulse welding. The gap may retain dirt, debris and/or moisture if it is not sealed. The moisture can be particularly problematic as it can begin to corrode one or both of the materials of the two components. If the moisture is comprised of salt water, such as found on a salted roadway, for example, the salt water can function as an electrolyte between the materials of the two components, especially if the materials of the two components are dissimilar. An electrolytic solution can cause corrosion to begin and the corrosion will continue if left untreated.

Corrosion at the gap initially results in a degraded appearance. If the corrosion is not dealt with, it can compromise the connection between the tube and the fitting, thus permitting moisture, dirt and debris into the gap. After prolonged exposure, the weld could become compromised.

In order to prevent moisture from entering or residing in the gap, a coating or a corrosion barrier can be applied to the gap. The coating prevents moisture, dirt and debris from reaching the gap. As a result, the gap does not experience corrosion and it does not become degraded.

The prior art usually address this issue by painting a sealant over the joint area. For example U.S. Patent No. 6,389,697 recognizes that the magnetic pulse welding process joins aluminum and steel materials and that the interface has to be protected from corrosion due to galvanic action. The patent indicates "[tjhese concerns are easily addressed using conventional painting or sealing techniques in the joint areas." U.S. Patent No. 6,908,024 and U.S. Patent Application Publication No. 2005/0035586 which both deal with magnetic pulse welding of dissimilar materials, indicate that a corrosion inhibitor can be added to welded surfaces. Lastly, U.S. Patent Publication No. 2012/0071250 discloses a spacer between an end fitting and a drive shaft. The publication indicates that a UV-cured urethane coating could be sprayed onto the spacer of the desired component of the driveshaft assembly and

subsequently cured with UV light.

However, most of the prior art deal with joints in vehicle frame members, while the present invention is preferably suited for a joint subjected to twisting and torque forces. It has also been found that the urethane coating can lose its effectiveness when exposed to corrosive environments. Therefore, the coating used here must be ductile enough to locate into the gap and have enough adherence to withstand difficult road or cleaning conditions and a corrosive environment.

The embodiments of the present invention elucidated below describe a method for preventing corrosion between two components, especially when those components are formed from dissimilar materials, as with a drive shaft tube component and end fitting component of a driveshaft assembly. The method may include coating a gap formed during magnetic pulse welding. The coating over the gap prevents corrosion due to galvanizing action between two dissimilar metals.

It has been discovered that by coating the gap at the weld interface of a driveshaft assembly in accordance with the preferred methods, the weld interface is better protected from exposure to the elements and is, therefore, better protected from corrosion.

SUMMARY OF THE INVENTION

A method for treating joined components. The method involves joining an end fitting into a driveshaft tube resulting in a gap between the two. The gap is cleaned and dried. As the joined end fitting and tube are rotated, a liquidized metal coating is applied. The coating fills the gap and extends laterally beyond the gap. A phenolic resin may then be applied over the coating. BRIEF DESCRIPTION OF THE DRAWINGS The above, as well as other advantages of the present invention, will become readily apparent to those skilled in the art from the following detailed description when considered in the light of the accompanying drawings in which:

FIG. 1 is an exploded perspective view of an end fitting and a driveshaft tube shown prior to being assembled and secured together by means of a magnetic pulse welding operation.

FIG. 2 is a further enlarged sectional elevational view showing portions of the end fitting and driveshaft tube prior to the commencement of the magnetic pulse welding operation.

FIG. 3 is an enlarged sectional elevational view showing portions of the end fitting and driveshaft tube after performance of the magnetic pulse welding operation.

FIG. 4 shows an assembly for providing a coating to a driveshaft assembly after performance of the magnetic pulse welding operation.

FIG. 5 is an enlarged sectional elevational view showing portions of the end fitting and driveshaft tube after performance of the magnetic pulse welding operation with the coating applied.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

It is to be understood that the invention may assume various alternative orientations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific assemblies, articles and features illustrated in the attached drawings, and described in the following specification are simply exemplary embodiments of the inventive concepts. Hence, specific dimensions, directions, or other physical characteristics relating to the embodiments disclosed are not to be considered as limiting, unless expressly stated otherwise.

Described herein is a method for preventing corrosion between two components. It has been found that when two components are joined together using magnetic pulse welding, a gap may result at the welding interface. If through the gap the weld between the components is exposed to certain environmental conditions, such as salt water, the salt water in the gap of the components can cause them to undesirably corrode. A method and apparatus are needed to prevent the corrosion.

Many components, such as driveshaft assembly components, are usually made of metals or metal containing materials, although the material used for the components should not be construed as being limited to metal or metal containing materials by this disclosure. Any suitable material, such as plastic as one non-limiting example, may be used. In driveshaft assemblies, such as the portion of the driveshaft assembly 10 shown in Fig. 1 , the driveshaft tube 20 and end fitting 30 may be made from different metals or metal containing materials different than each other. For instance, one of the components may be made from steel and the other from aluminum.

Sometimes it is this difference in materials used for the two components that can cause corrosion due to galvanizing effects in the presence of environmentally available electrolytes. One example of this is with a driveshaft tube 20 and end fitting 30 made from different materials. When the driveshaft assembly is exposed to salt water, such as from salt mixed with precipitation on winter roads, corrosion can occur at joints between the two components.

Fig. 1 shows an end fitting 30 and a driveshaft tube 20 shown prior to being assembled and secured together by means of a magnetic pulse welding operation. Although any end fitting can be used with the method of the present invention, Fig. 1 shows, by way of example only and not intending to be limiting, a yoke type end fitting 30.

Although this invention will be described and illustrated in the context of securing an end fitting 30 to a driveshaft tube 20 to form a portion of a driveshaft assembly 10, it will be appreciated that the apparatus and method of this invention can be used with any two or more components that are joined together for any desired purpose or application. It will also be appreciated that the invention can be used simply to fill a gap or void in any structure, whether that gap or void is created at the interface of two or more structures or if the gap or void is located anywhere within a unitary structure. The illustrated driveshaft tube 20 is generally hollow and cylindrical in shape and can be formed from any desired material, such as 6061 T6 aluminum alloy, for example. Preferably, the driveshaft tube 20 is substantially cylindrical with uniform wall thickness, although such is not required. The driveshaft tube 20 has an end portion 21 that terminates at an end surface 22.

The illustrated end fitting 30 is a tube yoke formed from a material that can be either the same as or different from the material used to form the driveshaft tube 20, such as steel or an alloy of aluminum, for example. The end fitting 30 as shown in Fig. 1 may have a body portion 31 having a pair of opposed yoke arms 32 that extend therefrom in a first axial direction. A pair of aligned openings 33 are formed through the yoke arms 32 and are adapted to receive conventional bearing cups (not shown) of a universal joint cross therein. A generally hollow neck portion 34 extends axially in a second axial direction from the body portion 31.

FIG. 2 illustrates the structure of the neck portion 34 of the end fitting 30 in more detail, albeit in a somewhat exaggerated manner. As shown therein, the neck portion 34 of the end fitting 30 preferably has an outer surface including a first tapered portion 34a that tapers outwardly from a relatively small outer diameter adjacent to the body portion 31 to an outermost point 34b. The outer surface of the neck portion 34 further includes a second tapered portion 34c that tapers inwardly from the outermost point 34b to the axial end of the neck portion 34. However, it is also within the scope of the invention for the second portion 34c to be substantially the same radius as the point 34b. The outer surface of the neck portion 34 is preferably smaller in diameter than the outer diameter of the body portion 31. As a result, an annular shoulder 34d is defined between the neck portion 34 and the body portion 31 of the end fitting 30.

The outermost point 34b of the neck portion 34 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 21 of the driveshaft tube 20. Thus, when the end portion 21 of the driveshaft tube 20 is disposed about the neck portion 34 of the end fitting 30 as shown in FIG. 2, the two components are positively located relative to one another.

However, the outer diameter defined by the outermost point 34b of the neck portion 34 can, if desired, be somewhat smaller in diameter than the inner diameter defined by the inner surface of the end portion 21 of the driveshaft tube 20. The outer diameter can also be larger in diameter than the inner diameter so as to create an interference fit.

The second tapered portion 34c of the outer surface of the neck portion 34 is provided to facilitate the axial installation of the end portion 21 of the driveshaft tube 20 onto the neck portion 34 of the end fitting 30 in a known manner. The hollow neck portion 34 of the end fitting 30 may have a

substantially uniform wall thickness, although such is not required. This tapered outer surface of the neck portion 34a of the end fitting 30 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 34 of the end fitting 30 can be found in U.S. Pat. No. 5,981 ,921. The disclosure of that patent is incorporated herein by reference to the extent permitted by law.

While the above references one end fitting design, other end fitting designs are permissible. The present invention works equally well where any two components are put together and a gap results.

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

The end fitting 30 and tube 20 are located within a magnetic pulse welding machine. The machine and magnetic pulse welding (MPW) process may be as described in RE41 , 101 , 4,129,846 and 5,981 ,921 which are hereby incorporated by reference herein to the extent permitted by law.

The MPW process generates an immense and momentary

electromagnetic field about the end portion 21 of the driveshaft tube 20. The electromagnetic field exerts a very large force on the outer surface of the end portion 21 of the driveshaft tube 20, causing it to collapse inwardly at a high velocity onto the neck portion 34 of the end fitting 30, as shown in FIG. 3. The resulting impact of the inner surface of the end portion 21 of the driveshaft tube 20 with the outer surface of the neck portion 34 of the end fitting 30 causes a weld or molecular bond to occur therebetween, such as shown at the region 47 in FIG. 3.

The size and location of the weld region 47 will vary with a variety of factors, such as the size of the space 36, the size, shape, and nature of the materials used to form the driveshaft tube 20 and the end fitting 30, the size and shape of the inductor used in the magnetic pulse welding operation, the angle and velocity of the impact between the end portion 21 of the driveshaft tube 20 and the neck portion 34 of the end fitting 30, and the like. It will be appreciated that the illustrated weld region 47 is intended to be representative of an exemplary prime welding area that provides the best possible adherence of the driveshaft tube 20 to the end fitting 30, and that other areas of the driveshaft tube 20 and the end fitting 30 may also be welded together as well during this process.

In some cases, after the magnetic pulse welding process, a gap 50 remains at the interface between the end surface 22 of the drive shaft tube 20 and the shoulder 34d on the end fitting 30. The gap 50 is located on an external surface of the joined components. The gap 50 is substantially v-shaped and is circumferentially continuous about the abutment area. The gap 50 may, or may not, be airtight and/or watertight, but is typically large enough to retain dirt, debris and/or moisture.

The moisture can be particularly problematic as it can begin to corrode one or both of the materials used in the construction of the driveshaft tube 20 and end fitting 30. For example, if the moisture is comprised of salt water, the salt water can function as an electrolyte between dissimilar metals, if the components are comprised of metals. An electrolytic solution can cause corrosion to begin and it will continue if left untreated. Corrosion at the gap 50 initially results in a degraded appearance. If the corrosion is not dealt with, it can compromise the connection between the tube 20 and the end fitting 30, thus permitting moisture, dirt and debris into the gap 50. After prolonged exposure, the weld 47 could become compromised.

In order to prevent moisture from entering or residing in the gap 50, a coating 64 can be applied to the gap 50. The process of applying the coating 64 may begin with a cleaning step. The cleaning step may comprise removing any surface dirt, debris, contaminants, or liquids from the gap 50 or surrounding area. Many different cleaning steps might be used depending on the type of material that may be present on or in the gap 50 and the degree to which the material is located on or in the gap 50.

Preferably, the coating is applied to a new end fitting 30 and a new tube 20 that have been joined after the magnetic pulse welding process. Thus, the tube 20 and end fitting 30 are typically relatively clean. In some instances, grit blasting may be used as necessary to remove any debris from the end fitting 30, the tube 20 and/or the gap 50. It is recommended that the surface be finished to approximately 200 Ra. Other solvents/cleaners may additionally or alternatively be used without going beyond the bounds of the invention described herein.

The cleaner/solvent may be applied by hand using a wipe, such as a towel, with the cleaner/solvent located automatically or manually thereon. The wipe can then be located in contact in and about the gap 50 so that it is clean. It is also permissible for the cleaning step to be automated in whole or in part. For example, a pad can be automatically loaded with cleaner/solvent and then automatically applied to the gap 50. The loading step can be automated via a computer and the application step can also be automated by a computer to apply the same amount of cleaner/solvent to the desired area for a

predetermined time, pressure, etc.

A blowing/drying step may be used to further clean the gap 50 and/or to dry any cleaner/solvent or other liquids that remains on or in the gap 50. One example of how the blowing step can be achieved is shown in Fig. 4. In one embodiment, one or more dispensing heads 60 may direct pressurized air at the gap 50. The dispensing heads 60 may be stationary and the gap 50 may be rotated by them or the gap 50 may be stationary and the dispensing heads 60 move about it. Alternatively, there may be a plurality dispensing heads 60 positioned about the gap 50 so as to provide pressurized air entirely about the gap 50.

If the tube 20 is to be rotated, the tube 20 and its attached end fitting 30 can be located on a surface capable of supporting the tube 20 yet permitting it to rotate on the surface. One example of such as surface comprises a cradle 52 fitted with rollers 54 designed to contact and rotationally support the tube 20. One example of a cradle 52 is depicted in Fig. 4.

The end fitting 30 is connected to a source of rotation, such as an electric motor 56. The end fitting 30 may be connected to the motor 56, such as through the use of removable mechanical fasteners 58. The motor 56 and fasteners 58 are depicted in Fig. 4.

In an alternative embodiment, the dispensing head 60 can be used to dispense a coating. It is also within the scope of the invention for the coating to be applied using other means.

The coating 64 may be any material that can be deposited in and about the gap 50. Preferably, the coating 64 is in liquid form so that it can be sprayed on. One example of a coating 64 that may be used is a liquidized metal;

preferably the liquidized metal is a mixture of zinc and aluminum. The metal initially comes in the form of a wire with a zinc core and an aluminum outer casing. The outer aluminum casing protects the zinc core from oxidizing.

Once the wire is melted and sprayed onto the gap 50, the zinc acts as a sacrificial material, meaning any corrosion will attack the zinc due to its proprieties before attacking the underlying materials.

Regardless of the coating material used, it may be preferable to use a material that dries quickly, that does not detract from the appearance of the gap 50, and/or that can survive the extreme conditions that vehicle drive shafts are exposed to in the environment and elements.

The liquidized metal coating 64 comprised of aluminum and zinc has been found to meet all of the criteria listed above and it also provides galvanized protection.

The coating 64 can be applied manually and/or automatically. The coating 64 is uniformly applied entirely about the circumference of the gap 50 so that it completely fills the gap 50. The coating 64 is sprayed to a thickness of about 0.020 inches as measured from an outer surface of said end fitting and said driveshaft tube. Additionally, sufficient coating 64 is applied so that it extends laterally outward from the center of the gap 50.

Once the coating application is completed and allowed to cool, a phenolic resin 66 may then be applied. The resin 66 may also be applied manually and/or automatically. The resin 66 is then air cured for approximately 30 to 60 minutes. The resin 66 acts as a sealant to seal the pores of the liquidized metal coating 64. It also prevents the exterior granular structure of the liquidized metal coating 64 from coming off and contaminating other driveline components, such as booted areas that contain grease.

The resulting coating 64 and resin 66 application is preferably smooth and free of visible contaminants and defects including porosity, craters, bubbles, blisters, tears and peeling. If desired, additional coating layers can be applied over the initial coating layer, or at different locations along the shaft using the same process as described above.

The coating 64 prevents moisture, dirt and debris from reaching the gap

50. As a result, the gap 50 does not experience corrosion and the weld 47 does not become degraded. Fig. 5 shows the driveshaft tube 20 and end fitting 30 after being welded and after the coating 64 and the resin 66 have been applied to the gap 50.

From the foregoing detailed description, it will be apparent that various modifications, additions, and other alternative embodiments are possible without departing from the true scope and spirit. The embodiments discussed herein were chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to use the invention in various embodiments and with various modifications as are suited to the particular use contemplated. As should be appreciated, all such modifications and variations are within the scope of the invention.

Claims

WHAT IS CLAIMED:

1. A method for treating joined components, comprising the steps of: joining an end fitting into a driveshaft tube resulting in a gap between said end fitting and said driveshaft tube;

cleaning said gap of said joined end fitting and said driveshaft tube; drying said gap of said joined end fitting and said driveshaft tube;

rotating said joined end fitting and said driveshaft tube together;

applying a liquidized metal coating to said gap of said rotating joined end fitting and said driveshaft tube, said coating completely fills said gap and extends laterally outward beyond said gap;

allowing said liquidized metal to cool; and

applying a phenolic resin over said liquidized metal coating, said resin is applied directly over said liquidized metal coating and then air cured.

2. The method of claim 1 , wherein said gap is located where an end surface of an end portion of said driveshaft tube abuts a shoulder of said end fitting, said should is defined as the transition area between the neck portion and the body portion of said end fitting, said gap is substantially v-shaped and is circumferentially continuous about said joined components.

3. The method of claim 1 , wherein said liquidized metal is comprised of aluminum and zinc.

4. The method of claim 1 , wherein in a first state said liquidized metal is a wire with a zinc core and an aluminum outer casing, wherein in a second state said wire is melted to create said liquidized metal that can be sprayed on said driveshaft tube and end fitting and in said gap.

5. The method of claim 1 , wherein said end fitting and said driveshaft tube are constructed of different materials.

6. The method of claim 1 , wherein said liquidized metal is sprayed to a thickness of at least 0.020 inches as measured from an outer surface of said end fitting and said driveshaft tube.

7. The method of claim 1 , wherein said end fitting and said driveshaft tube are cleaned by grit blasting.

8. The method of claim 1 , wherein said end fitting and said driveshaft tube are cleaned by hand wiping with a solvent soaked towel or wipe.

9. The method of claim 1 , wherein said end fitting and said driveshaft tube are dried by forcing pressurized air through dispending heads.

10. The method of claim 3, wherein said liquidized metal prevents corrosion by an electrolytic solution of a joined end fitting and a driveshaft tube formed of different materials.

11. The method of claim 3, wherein said zinc acts as a sacrificial material.

12. The method of claim 1 , wherein filling said gap with said liquidized metal coating prevents foreign objects from entering said gap.

13. The method of claim 1 , wherein said phenolic resin acts as a sealant to seal the pores of said liquidized metal coating.

14. A bimetallic driveshaft assembly comprising:

a driveshaft tube, said driveshaft tube is generally hollow and cylindrical in shape, said driveshaft tube comprising an end portion that terminates at an end surface;

an end fitting, said end fitting comprising a pair of opposed yoke arms extending in a first axial direction and a generally hollow neck portion extending in a second axial direction, said neck portion slidably engaged with said end portion of said driveshaft tube, wherein said neck portion of said end fitting is located within said end portion of said driveshaft tube; and

a gap located circumferentially at the intersection of said driveshaft tube and said end fitting.

15. A bimetallic driveshaft assembly according to claim 14, wherein said gap is filled with a liquidized metal.

16. A bimetallic driveshaft assembly according to claim 15, wherein in a first state said liquidized metal is a wire with a zinc core and an aluminum outer casing, wherein in a second state said wire is melted to create said liquidized metal that can be sprayed on said driveshaft tube and end fitting and in said gap.

17. The method of claim 15, wherein said liquidized metal is sprayed to a thickness of at least 0.020 inches as measured from an outer surface of said end fitting and said driveshaft tube.

18. A bimetallic driveshaft assembly according to claim 15, wherein a phenolic resin is applied over said liquidized metal, said phenolic resin is air cured.