A bearing includes an inner ring having an outer surface defining a first pocket therein. The surface of the first pocket can be provided with a first conductive coating. The bearing includes an outer ring concentric with and radially outward from the inner ring. The outer ring has an inner surface defining a second pocket therein, and a surface of the second pocket can be provided with a second conductive coating. A plurality of rolling elements are disposed between the inner ring and the outer ring. An electrically-conductive shunt ring assembly couples the inner ring to the outer ring and is configured to inhibit electrical current passing between the inner ring and outer ring from passing through the rolling elements. The shunt ring assembly is sized and configured to enable lubricant to flow freely through the bearing. In some embodiments, the shunt ring is a conductive snap ring.

TECHNICAL FIELD

The present disclosure relates to an electrical shunt formed integral or assembled within a bearing. In particular, the electrical shunt may be specifically designed for wet (non-sealed) bearing, such as a bearing subjected to lubricant such as automatic transmission fluid.

BACKGROUND

Bearings are used in a plethora of applications in which relative rotation is desired between two coaxial components. Bearings such as roller bearings may include an inner ring with a raceway, an outer ring with a raceway, and a plurality of rolling elements (e.g., balls) between the raceways. In some applications, the bearings are sealed such that no fluid, debris, etc. is able to enter the raceways and impair the operability of the bearing. In other applications, the bearings are not sealed (open) to allow fluid (e.g., lubricant) to pass through the bearing during operation. Both sealed and non-sealed bearings alike can be used in applications in which electrical current (leakage current) is present. These leakage currents, if not properly grounded or diverted, can impair the operability of the bearing or cause damage. If this occurs frequently, bearings may have to be replaced at regular intervals and repairs can get expensive.

SUMMARY

According to one embodiment, a bearing includes an inner ring extending about an axis and having an outer surface defining a first pocket therein, wherein a surface of the first pocket is provided with a first conductive coating. The bearing includes an outer ring concentric with and radially outward from the inner ring, the outer ring having an inner surface defining a second pocket therein, wherein a surface of the second pocket is provided with a second conductive coating. A plurality of rolling elements are disposed between the inner ring and the outer ring. An electrically-conductive shunt ring assembly couples the inner ring to the outer ring and is configured to inhibit electrical current passing between the inner ring and outer ring from passing through the rolling elements. The shunt ring assembly is sized and configured to enable lubricant to flow freely through the bearing, and the shunt ring assembly contacts the first and second conductive coatings.

In yet another embodiment, a bearing includes an inner ring extending about an axis and having an outer surface that defines an inner raceway of the bearing, wherein the outer surface is provided with a first conductive coating that does not cover the inner raceway. The bearing includes an outer ring concentric with and radially outward from the inner ring, the outer ring having an inner surface that defines an outer raceway of the bearing, wherein the inner surface is provided with a second conductive coating that does not cover the outer raceway. A plurality of rolling elements are disposed between the inner ring and the outer ring. An electrically-conductive shunt ring assembly couples the inner ring to the outer ring and is configured to inhibit electrical current passing between the inner ring and outer ring from passing through the rolling elements. The shunt ring assembly is sized and configured to enable lubricant to flow freely through the bearing, and the shunt ring assembly contacts the first and second conductive coatings.

In yet another embodiment, a bearing includes an inner ring extending about an axis and having an outer surface defining a first pocket therein. An outer ring is concentric with and radially outward from the inner ring, and the outer ring has an inner surface defining a second pocket therein. A plurality of rolling elements are disposed between the inner ring and the outer ring. An electrically-conductive shunt ring assembly couples the inner ring to the outer ring and is configured to inhibit electrical current passing between the inner ring and outer ring from passing through the rolling elements. The shunt ring assembly is sized and configured to enable lubricant to flow freely through the bearing. The shunt ring assembly includes a non-continuous shunt ring engaged to one of the inner ring and the outer ring via a snap fit within one of the first pocket and second pocket.

DETAILED DESCRIPTION

Directional terms used herein are made with reference to the views and orientations shown in the exemplary figures. A central axis is shown in the figures and described below. Terms such as “outer” and “inner” are relative to the central axis. For example, an “outer” surface means that the surfaces faces away from the central axis, or is outboard of another “inner” surface. Terms such as “radial,” “diameter,” “circumference,” etc. also are relative to the central axis.

FIG. 1Aillustrates a cross-sectional view of an assembled bearing10, andFIG. 1Billustrates an exploded perspective view of the bearing10. The components shown in these Figures are base components similar to the bearing disclosed in U.S. patent application Ser. No. 15/837,220, which is hereby incorporated by reference in its entirety. The teachings described below can be implemented in any roller bearing, and the ones shown herein are merely exemplary. The bearing10shown in these Figures also does not show the conductive shunt assembly or coatings that are disclosed in the remaining Figures. The bearing10includes an outer ring12and an inner ring14. Each ring extends about a central axis16. The outer ring12has an inner surface facing the central axis16that defines a concave outer raceway18facing the axis16. Likewise, the inner ring14has an outer surface facing away from the central axis16that defines a concave inner raceway20facing away from the axis16.

In the illustrated embodiment, the bearing is a rolling element bearing having a plurality of rolling elements22. However, in other embodiments, the bearing is a non-rolling element bearing, such as a plain bearing, a flexure bearing, etc. The rolling elements22are shown as spherical ball rolling elements. In other embodiments, the rolling elements are other shapes such as cylindrical, spherical, frustoconical, and other shapes appreciable by those skilled in the art. The rolling elements22rest between and contact the raceways of the outer ring12and the inner ring14. In one embodiment, the rolling elements22are mounted within, and retained, and can fully rotate via a cage24. The cage24reduces friction, wear, and bind by preventing the rolling elements22from rubbing against each other during operation of the bearing10. The rolling elements22enable relative rotational movement between an outer element (not shown) connected to the outer ring, and an inner element (not shown) connected to the inner ring. The embodiment shown here may be one in which the outer ring is stationary and the inner ring rotates relative to the outer ring.

Rolling element bearings in automotive applications may be subject to electrical current (leakage currents) passing through, seeking ground. This can particularly occur in hybrid vehicles, for example with a bearing for the electric motor. Electric arcing through the bearing raceways and rolling elements can cause electric discharge machining (EDM) damage. Over time, this has the potential to degrade the quality of the rolling elements and raceways of the bearing. Some bearing applications require lubricants, such as automatic transmission fluid (ATF), to be able to pass through the bearing. These are known as wet or non-sealed bearings.

If a leakage current passes continuously through a non-sealed bearing running in the presence of a lubricant, depending on the dielectric strength of the lubricant, after a certain shaft voltage is reached, the leakage current can break through the lubricant if unaccounted for. Rolling motion of the rolling elements subjected to these leakage currents can cause electrical arcing and change the material structure. This can lead to frosting of the rolling elements fluting on the raceways. If this phenomenon continues for a prolonged period, rolling elements and raceway surfaces roughen, untempered martensite can form on the circumference of the raceways (rehardened zones can be observed microstructurally), bearing can become noisy and can have an increased probability of pre-mature failure.

Therefore, according to various embodiments of this disclosure, the bearing disclosed herein is a non-sealed bearing having a shunt device or shunt assembly to safely bypass electric current around the bearing raceways and rolling elements to ground while still enabling a free flow of lubricant across the bearing. The remaining Figures (FIGS. 2A-6) show the bearing provided with such a shunt device or shunt assembly.

Parts of the bearing10ofFIGS. 1A-1Bare implemented into the remaining Figures, such as the inner ring, the outer ring, the rolling elements, and the cage. While new reference numbers are used in the remaining Figures, the description ofFIG. 1A-1Bcan be implemented into the embodiments of the remaining Figures with certain modifications, such as grooves to accommodate the shunt assembly.

FIG. 2Ashows a front plan view of part of a bearing30,FIG. 2Bshows a cross-sectional view of the bearing30, andFIG. 2Cis an enlarged view of region2C ofFIG. 2B. The bearing30includes an outer ring32and an inner ring34. Each ring extends about a central axis36. The outer ring32has an inner surface facing the central axis36that defines a concave outer raceway38facing the axis36. Likewise, the inner ring34has an outer surface facing away from the central axis36that defines a concave inner raceway40facing away from the axis36. A plurality of rolling elements42are bound by a cage44and enable relative rotation between the inner ring34and the outer ring32.

A shunt assembly50(also referred to as a shunt ring assembly) is configured for assembly within the bearing30, and is shown in isolation inFIG. 3. The shunt assembly50includes an annular ring52(also referred to as a shunt ring) extending about the axis36. The ring52may be a continuous ring (as shown inFIG. 3) formed by stamping, for example. Alternatively, the ring may be a non-continuous ring with a small break (as shown inFIGS. 5-6, described below). The shunt ring52is conductive, and can be made of any metal such as steel, for example. The shunt ring52may have a flange54that extends inward toward the axis36. The flange54is provided to solder the ferrules (explained below) and inhibit or prevent potential damage to the soldered ferrules (explained below) during assembly of the shunt ring assembly50to the bearing30.

The shunt ring assembly50is also provided with a plurality of ferrules56extending inwardly from an inner surface of the ring52. The ferrules56can be conductive, also made of metal such as steel, copper or its alloys. In one embodiment, the ferrules56are soldered to the flange54if ferrules56and the flange54are made of dissimilar metals. The ferrules56can also be welded if both the shunt ring52and the ferrules56are ferrous. Each of the ferrules56holds a plurality of fibers, such as carbon fibers58which are also conductive. During assembly, the carbon fibers58may be crimped to the ferrules56(such as by the method disclosed in U.S. patent application Ser. No. 15/837,220, and then each ferrule56with crimped fibers58can be soldered to the flange54of the ring52. Alternatively, the ferrules56can first be soldered or welded to the flange54of the ring52, and thereafter the fibers58can be crimped or otherwise attached to each ferrule56.

After assembly, the ferrules56extend slightly below the pitch diameter of the bearing30. In other words, the rolling elements42can collectively define a pitch diameter extending through the center of the rolling elements42. The ferrules56each extend closer to the center axis36than the center of the rolling elements42. This minimizes flexing on the ferrules56and potential breakage of the conductive fibers58.

FIG. 3shows forty conductive ferrules56, each with multiple conductive carbon fibers58crimped therewith. This is merely for illustration purposes. In other embodiments, more or less than forty ferrules56can be provided, depending on the size requirements of the bearing without restricting the lubrication flow.

In one embodiment, the shunt ring assembly50can be fitted within grooves or shoulders in the inner and outer rings of the bearing, and then tack welded at70. For example, referring toFIGS. 2A-4B, the outer ring32may be provided with a recess60that may extend axially all the way to an axial face62of the outer ring32. The inner ring34may be provided with a groove64that extends radially outward from an inner surface66of the inner ring34. In the illustrated embodiment, the groove64does not extend axially all the way to an axial face68of the inner ring34. The terms “recess” and “groove” are used herein to differentiate the shapes of the contours etched from the inner and outer rings, but these features can more generally be referred to as “pockets” which would include either a recess or a groove illustrated herein.

The outer surface of the ring52can be fitted within the recess60and connected thereto via tack welding, with tack welds shown generally at70. The location of the tack welds70may be spaced annularly about the axis36, and in the illustrated embodiment four tack welds70are provided. The tack welds70can ensure an effective circumferential contact between the ring52and the outer ring32, for example if the ring52or the recess60are not sufficiently round or matching in shape. This can effectively bypass the leakage current to the outer ring32when appropriately grounded. The tack welding may be performed with compatible metals. The innermost portion of the fibers58contact the inner ring34within the groove64. The groove64on the inner ring34may extend as deep as half of the thickness of the inner ring34. In other words, the groove64may extend a quarter of the way through the inner ring34. This allows the groove64to be configured to prevent the carbon fibers58from potentially losing contact with the inner ring34and keep the fibers58out of the raceway if they were to pop out of the groove64.

The surfaces of the outer ring32that define the recess60may be coated with a conductive coating72. Likewise, the surfaces of the inner ring34that define the groove64may be coated with a conductive coating74. The coatings72,74may be extremely thin, in the range of microns.FIGS. 4A and 4Bhave enlarged the coatings72,74for illustrative purposes. The conductivity of the coatings72,74can ensure a superior conductivity for the leakage current passing through the shunt assembly50between the inner and outer rings. The coatings72,74may be copper or silver, for example, due to their properties of providing minimal electrical resistance compared to bearing steel. While the coatings72,74are illustrated as covering the surfaces that define the recess60and the groove64, the coatings72,74may also be present in other areas of the outer surface of the inner ring and the inner surface of the outer ring, except not in areas of the raceway. Having a conductive coating in the raceway may interfere with operation of the rolling elements, including flaking off and hindering rolling of the rolling elements; further, the electrical current is intended to be diverted away from the raceway, so the conductive coating in the raceways may counter that goal.

The ring52may have a slight press fit or snug fit or slip fit within the recess60of the outer ring32. A snug fit may minimize any possible damage to the shunt ring assembly50during assembly without flaking the conductive coating72off of the outer ring32. Therefore, an interference fit may not be desirable in certain embodiments in which the layer of coating72is relatively thin.

FIG. 5illustrates another embodiment of a shunt ring assembly50′. In this embodiment, the shunt ring52′ is a non-continuous ring with a small break80between a pair of open ends82,84facing one another. The break80is enlarged for illustrative purposes inFIGS. 5-6, and may be smaller than that shown. The ring52′ can be flexible, and can be slightly larger in diameter than the recess60when the ring52′ is not forced to constrict (e.g., left in an undisturbed state). During assembly, the ring52′ can act as a snap ring in which an operator can constrict the ring52′ and insert the ring52′ into the recess60, and let go of the ring52′ so that the ring52′ is biased to expand outward into fit with the outer ring32. In short, the ring52′ can be biased outwardly in a snap-fit engagement.

FIG. 6illustrates another embodiment of a shunt ring assembly50″ having the same type of snap-fit ring52′ and break80. This embodiment illustrates that the shunt ring assembly50″ can be provided with the ferrules56′ that are connected to the ring52′ in sets of multiple numbers, such as two. In other embodiments the ferrules can be soldered or welded to the ring in sets of three. These embodiments in which sets of ferrules are attached to the ring does not necessary require an increased number of ferrules in the assembly, as the same number of ferrules can be used but just arranged differently (e.g., in sets instead of individually).

It should be understood that the illustrations described above are merely exemplary. Other embodiments exist in which the components are rearranged. For example, the shunt assembly50can be reversed such that the ferrules extend radially outward from the outer surface of the ring. In that embodiment, the fibers would touch the outer ring of the bearing rather than the inner ring. The groove and the recess may be reversed in their respective location amongst the outer ring and the inner ring to accommodate this. Moreover, if the shunt ring is a snap-ring as described in embodiments above, the spring bias of the ring may be reversed such that it snaps and is biased inward so that the snap ring snaps to the inner ring of the bearing rather than the outer ring. This may be advantageous for embodiments in which the inner ring is stationary and the outer ring moves relative to the inner ring.

PARTS LIST

The following is a list of reference numbers shown in the Figures. However, it should be understood that the use of these terms is for illustrative purposes only with respect to one embodiment. And, use of reference numbers correlating a certain term that is both illustrated in the Figures and present in the claims is not intended to limit the claims to only cover the illustrated embodiment.10bearing12outer ring14inner ring16central axis18outer raceway20inner raceway22rolling element24cage30bearing32outer ring34inner ring36central axis38outer raceway40inner raceway42rolling element44cage50shunt assembly or shunt ring assembly50′ shunt assembly or shunt ring assembly50″ shunt assembly or shunt ring assembly52ring or shunt ring52′ ring or shunt ring54flange56ferrule56′ ferrule58conductive fibers60recess62axial face64groove66inner surface68axial face70tack weld72conductive coating74conductive coating80break or slit82open end84open end