WO2025083378A1

WO2025083378A1 - Apparatus for bearing assembly

Info

Publication number: WO2025083378A1
Application number: PCT/GB2023/052680
Authority: WO
Inventors: Ramin RAHMANI; Matthew Simpson
Original assignee: Loughborough University
Current assignee: Loughborough University
Priority date: 2023-10-16
Filing date: 2023-10-16
Publication date: 2025-04-24
Anticipated expiration: 2026-04-16

Abstract

Certain examples of the present disclosure relate to an apparatus (10), for use in a bearing assembly (1) comprising at least one bearing element (20), the apparatus (10) comprising: means (100) for receiving the at least one bearing element (20), the receiving means (100) comprising: a first area (101) defining an area of contact with the bearing element (20), and a second area (102) adjacent the first area; wherein the second area (102) comprises a plurality of surface texture features (102ST); and wherein the first area (101) is substantially devoid of surface texture features.

Description

APPARATUS FOR BEARING ASSEMBLY

TECHNOLOGICAL FIELD

Examples of the present disclosure relate to an apparatus for a bearing assembly. Some examples, though without prejudice to the foregoing, relate to an apparatus for a bearing assembly configured for use in an elastohydrodynamic lubrication regime.

BACKGROUND

Conventional bearings or bearing assemblies are not always optimal.

In some circumstances it can be desirable to improve the tribological performance, e.g. reduce friction and/or reduce wear, of bearing assemblies. A reduction of friction can enhance energy efficiency of bearings/bearing assemblies and systems comprising the same. A reduction in wear can increase component life span and durability, which may also enhancing resource efficiency as well as reduce system downtime (e.g. in repairing/replacing components).

In some circumstances it can be desirable to improve the tribological performance of bearing assemblies working under elastohydrodynamic lubrication mechanism.

The listing or discussion of any prior-published document or any background in this specification should not necessarily be taken as an acknowledgement that the document or background is part of the state of the art or is common general knowledge. One or more aspects/examples of the present disclosure may or may not address one or more of the background issues.

BRIEF SUMMARY

The scope of protection sought for various embodiments of the invention is set out by the claims.

According to various, but not necessarily all, examples of the disclosure there are provided examples as claimed in the appended claims. Any examples and features described in this specification that do not fall underthe scope of the independent claims are to be interpreted as examples useful for understanding various embodiments of the invention.

According to at least some examples of the disclosure there is provided an apparatus for use in a bearing assembly comprising at least one bearing element, the apparatus comprising: means for receiving the at least one bearing element, the receiving means comprising: a first area defining an area of contact with the bearing element, and a second area adjacent the first area; wherein the second area comprises a plurality of surface texture features; and wherein the first area is substantially devoid of surface texture features.

According to at least some examples of the disclosure there is provided a bearing element, for use in a bearing assembly comprising means for receiving the at least one bearing element, the bearing element comprising: a first area defining an area of contact with the means for receiving the at least one bearing element, and a second area adjacent the first area; wherein the second area comprises a plurality of surface texture features; and wherein the first area is substantially devoid of surface texture features.

According to various, but not necessarily all, examples of the disclosure there is provided a bearing assembly, module, device and/or system comprising the above-mentioned apparatus and/or bearing element.

According to various, but not necessarily all, examples of the disclosure there is provided a method of providing and/or manufacturing an apparatus, a bearing element, a device and/or system as described herein.

According to various, but not necessarily all, examples of the disclosure there is provided a method of using an apparatus, a bearing element, a device and/or system as described herein.

The following portion ofthis 'Brief Summary’ section describes various features that can be features of any of the examples described in the foregoing portion of the 'Brief Summary' section mutatis mutandis. The description of a function should additionally be considered to also disclose any means suitable for performing that function, or any instructions stored in at least one memory that, when executed by at least one processor, cause an apparatus to perform that function.

In some but not necessarily all examples, the first area defines at least one of the following: a contact footprint; a contact footprint path; a surface area of the receiving means which, during use, is contacted by the bearing element; a bearing surface; a contact footprint path; a running track; and a contact patch.

In some but not necessarily all examples, the second area defines an area that is at least one of: non-overlapping with the first area; immediately adjacent to the first area; and located on a first and/or second side of the first area.

In some but not necessarily all examples, the plurality of surface texture features comprises at least one of the following: one or more surface modifications; one or more protrusions; one or more recesses; one or more reservoir means for receiving and/or storing a lubricant; a coating; a solid lubricant; and a porous material.

In some but not necessarily all examples, the second area has a different surface topography to the first area.

In some but not necessarily all examples, the apparatus is a race for the at least one bearing element of the bearing assembly.

In some but not necessarily all examples, the apparatus is a component in a bearing assembly configured for use in an elastohydrodynamic lubrication regime.

In some but not necessarily all examples, the apparatus is a component in at least one of: a rolling element bearing assembly, a constant velocity joint, a gear contact, a load bearing contact, and a biological prosthetic surfaces.

According to at least some examples of the disclosure there is provided a bearing assembly comprising: the apparatus as described above and at least one bearing element.

In some but not necessarily all examples, the bearing element is a rolling element bearing.

In some but not necessarily all examples, the bearing assembly is a lubricated bearing assembly.

In some but not necessarily all examples, the bearing assembly is configured for use in an elastohydrodynamic lubrication regime.

In some but not necessarily all examples, the bearing assembly is at least one of: a rolling element bearing assembly, a constant velocity joint, a gear contact, a load bearing contact, and a biological prosthetic surfaces.

While the above examples of the disclosure and optional features are described separately, it is to be understood that their provision in all possible combinations and permutations is contained within the disclosure. It is to be understood that various examples of the disclosure can comprise any or all of the features described in respect of other examples of the disclosure, and vice versa.

BRIEF DESCRIPTION OF THE DRAWINGS

Some examples will now be described with reference to the accompanying drawings in which:

FIG. 1 schematically illustrates a cross-sectional side on view of an example of the subject matter described herein;

FIG. 2 schematically illustrates a plan view of the example of FIG. 1 ;

FIG. 3 schematically illustrates a cross-sectional side on view of another example of the subject matter described herein;

FIG. 4 is an image of a first test track surface with no surface texture features applied;

FIG. 5 is an image of a second test track surface with surface texture features applied outside a contact track in accordance with examples of the subject matter described herein; FIG. 6 is an image of a third test track surface with surface texture features applied inside a contact track;

FIG. 7 is a graph of traction coefficient measurements against entrainment speed for the first test track surface of FIG. 4;

FIG. 8 is a graph of traction coefficient measurements against entrainment speed for the second test track surface of FIG. 5; and

FIG. 9 is a graph of traction coefficient measurements against entrainment speed for the third test track surface of FIG. 6.

The figures (in particular figures 1 to 3) are not necessarily to scale. Certain features and views of the figures can be shown schematically or exaggerated in scale in the interest of clarity and conciseness. For example, the dimensions of some elements in the figures can be exaggerated relative to other elements to aid explication. Similar reference numerals are used in the figures to designate similar features. For clarity, all reference numerals are not necessarily displayed in all figures.

DETAILED DESCRIPTION

The description relates to an apparatus 10, for use in a bearing assembly comprising at least one bearing element 20, the apparatus 10 comprising: means 100 for receiving the at least one bearing element 20, the receiving means 100 comprising: a first area 101 defining an area of contact with the bearing element 20, and a second area 102 adjacent the first area 101; wherein the second area 102 comprises a plurality of surface texture features 102ST; and wherein the first area 101 is substantially devoid of surface texture features.

FIGs. 1 and 2 respectively schematically illustrate a side-on cross sectional view, and a plan view, of an example of an apparatus 10 in accordance with the present disclosure. The apparatus 10 is for use in a bearing assembly 1 , i.e. the apparatus may be a part of/component of the bearing assembly. The bearing assembly further comprises at least one bearing element 20 (shown in dotted outline).

In the example shown, the bearing assembly is a lubricated rolling element bearing assembly, and the rolling element bearing is a ball bearing. In various examples, the bearing assembly/contacts could be lubricated by a lubricating grease, or a lubricant such as, but not limited to, mineral or synthetic base or fully formulated oils. The lubricant could be a fluid, semi-fluid or a solid (not least such as graphite).

The apparatus comprises means 100 for receiving the bearing element. Such means may comprise: a means for seating the bearing element not least such as a surface 100 for receiving and/or seating the bearing element. The apparatus may be made of any suitable material, not least for example steel.

The surface 100 comprises: a first area 101 defining an area of contact with the bearing element 20, and a second area 102 adjacent the first area.

A plurality of surface texture features 102ST are provided/applied to the second area 102. Whereas the first area 101 is substantially devoid of surface texture features. The first area 101 being substantially devoid of surface texture features may correspond to: a majority of the first area being devoid of surface texture features, and/or a main central portion/band of the first area being devoid of a surface texture features.

The surface texture features may comprise one or more microscale or nanoscale features created on/applied to the second area. In some examples, the surface texture features are engineered or machined features that are specially created/provided to the second area so as to modify its surface topography; whereas no such surface texture features are created/applied to the first area

The surface texture features may be one or more of the following: one or more surface modifications; one or more protrusions; one or more recesses; one or more reservoir means for receiving and/or storing a lubricant; a coating; a solid lubricant; and a porous material.

It is to be appreciated that various values of: geometric parameters of the surface features (e.g. texture feature: dimensions, width, length, depth, cross-sectional profile, base profile, shape), and distribution parameters of the surface features (e.g. distance between surface texture features in different directions, array patterns) could be selected as appropriate, e.g. as befitting the application/real-life use case of the apparatus.

The provision of surface texture features to the second surface may comprise artificially creating (e.g. in nano or microscale) surface features. These may be applied to the surface via any appropriate technique, not least such as: mechanical indentation, mechanical abrasion means, lithography techniques, and through use of lasers (e.g. laser surface texturing).

The surface texture feat ures/surf ace modification applied may be any feature (both micro and nanoscale features) that can act as reservoir for lubricant (i.e. to replenish the first area/contact footprint with lubricant when lubricant/oil starvation takes place). Additionally or alternatively, the surface texture features/surface modification applied may be any feature (both micro and nanoscale features) that perturbs a flow of lubricant outside of the first area/contact footprint - such as use of artificially created dents or cavities, as well as protrusions.

In some examples, the surface texture features could be generated through applying a special material, such as coatings on the surface of the second area outside of the first area/contact footprint. Some coatings have properties such as porosity. Such porosity features may act as lubricant reservoirs and may also produce micro or nano-bearing effects, resulting in pressure perturbations in that area and may contribute to the load carrying capacity of the bearing element. In addition, the surface texture features could be a specially designed surface roughness profile outside of the first area/contact footprint. For instance, through a use of different (or combinations of) machining, polishing, or grinding techniques advantages similar to the textured surfaces can be provided (e.g., by having dominant roughness valley features that can act as lubricant reservoirs).

As will be discussed in further detail below, not least with regards to FIGs 4 to 9, the inventors of the present application have realised that the such positioning of surface texture features in a particular location (namely applying surface texture features to an area outside of, but in close proximity to, the first area, i.e. a contact patch/contact footprint) surprisingly and advantageously gives rise to improved tribological performance (e.g. as compared to: the use of no surface texture features at all, or the application of a surface texture features in the contact area itself).

Furthermore, advantageously, the positioning of the surface texture features outside the first area/contact footprint means the surface texture features do not wear during operation of the bearing assembly (e.g. a rolling element bearing would not roll over and wear the surface texture features). Therefore, the benefit provided by such carefully positioned surface texture features should last longer than if the surface texture features were applied over the first area/contact footprint. In the prior art, the surface texture features may be positioned within the contact footprint and hence, during operation in high-pressure/heavy loading (not least for example above 200 or 500 MPa) applications, such positioned surface texture features can be potentially worn away - leading to a limited lifetime for any benefits provided by such positioned surface texture features.

Some, but not necessarily all, examples of the present disclosure may be applicable to mechanical systems in which relatively high pressure lubricated contacts occur. Such contacts are normally categorised as contacts which are subject to elastohydrodynamic lubrication (often abbreviated as EHD or EHL). Examples of the disclosure could be applied to rolling element bearings, which are often encountered in a wide range of machinery and applications. Examples could also be applied to other systems with similar contact conditions, such as for example: components such as constant velocity joints (e.g., in automotive drivetrain applications), gear contacts (e.g., in automotive or wind turbine or aerospace related gearboxes), load bearing contacts (e.g., in engines valvetrain (cam/roller contact)), and biological prosthetic surfaces (e.g., knee joint replacements).

Some, but not necessarily all, examples of the present disclosure may be applicable to mechanical systems which are not subject to EHL.

The first and second areas may be configured such that the second area has a different topography than the first area (e.g. due to the surface texture features/surface modification applied thereto). The second area may have a different (e.g. a higher or lower) surface roughness than the first area. The different surface roughness may correspond to having different surface profile measurement value(s) or different value(s) of profile roughness parameters for the second area than the first area. The surface roughness may be measured via any suitable method, not least such as that set out in BS EN ISO 4287:2000 British standard or ISO 4287:1997 standard.

In some examples, the apparatus is a component in a bearing assembly that is configured for use in an elastohydrodynamic lubrication regime.

For a lubricated bearing assembly operating above a certain contact pressure threshold, an exponential increase in the viscosity of the lubricant (several orders of magnitude) may radically alter the lubricant’s physical behaviour. The lubricant may change state, and behave in a manner closer to that of a solid than a fluid. A complete separation of contact surfaces may arise by an elastic deformation of the opposing contacting surfaces, under the action of the lubricant that has become extremely viscous. This creates the conditions called elastohydrodynamic regime. The physical behaviour of the lubricant and the opposing surfaces being radically different in the elastohydrodynamic regime.

In use, under high loading conditions and elastohydrodynamic conditions, contacting bodies (e.g. the bearing element 20 and the surface 100) may undergo elastic strain and deformation at their point of contact. This is schematically shown (in an exaggerated manner) with respect to the distorted shape of the lower portion of the bearing element that us in contact with the surface 100. Accordingly, rather than the bearing element having a rounded/circular lower portion and hence having point-like contact between the lower portion of the bearing element 20 and the surface 100, instead there is an extended/non- point-like flat area of contact between the lower portion of the bearing element 20 and the surface 100 due to the elastic strain/distortion - namely area 101 of the surface 100 and area 201 of the bearing element.

As is more clearly shown in FIG. 2, since, in use, the bearing element moves/rolls over the surface 100 (arrow 203 indicates a direction of motion of the bearing element), an instantaneous area of contact 101 , at one instance/point in time effectively moves/traces out a path or track defining a surface area 101 which, during use, is contacted by the bearing element. In the example illustrated in FIG. 2 (with a spherical bearing element and flat/planer surface 100) the instantaneous area of contact 101 , is shown as a circular contact area. However, it is to be appreciated that, in other examples, there may be differing shapes, forms and relative sizes of contact area. The instantaneous area of contact 101 i can take other shapes or forms not least for example elliptic or rectangular shapes such as may be commonly encountered in the contact mechanics and tribology.

Such a surface area 101 may be referred to as: a contact footprint, a contact footprint patch, a bearing surface, a contact footprint path, a running track, and/or a contact patch.

Such a surface area 101 may be defined as an area where contiguous surfaces (e.g. of the bearing element 20 and/or the surface 100 itself) may deform elastically due to developed high contact pressures, not least due to a lubricating fluid in that particular region under conditions of elastohydrodynamic lubrication/elastohydrodynamic lubrication regime.

In some examples, the second area defines an area that is at least one of: non-overlapping with the first area (i.e. the second area is separate and distinct from the first area); immediately adjacent to/in the immediate vicinity of the first area.

FIGs 1 and 2 show a projected area 202. In a similar manner to how an instantaneous area of contact 101 , (i.e. at one instance/point in time), during use and the course of movement/rolling of the bearing element over the surface 100, effectively sweeps out a path/track that corresponds to the first area 101 ; the projected area 202 likewise corresponds to a path/track of an instantaneous projection area 202, that the moving/rolling bearing element sweeps out during use. In the example illustrated in FIG. 2 (with a spherical bearing element and flat/planer surface 100) the instantaneous projection area 202i is shown as a circular projection area. However, it is to be appreciated that, in other examples, there may be differing shapes, forms and relative sizes of projection area. The instantaneous projection area 202, can take other shapes or forms not least for example elliptic or rectangular shapes such as may be commonly encountered in the contact mechanics and tribology.

In the example of FIGs 1 and 2, the second area 102 (and its surface texture features 102ST) are positioned/located sufficiently close/adjacent to the first area 101 such that the second area 102 lies within the projected area 202, but outside of the first area 101. In this regard, the second area 102 may figuratively be considered to be under the shadow of the bearing element’s projected area 202 but outside of the bearing element’s contact area 201 .

FIGs 1 and 2 show the second area 102, with its surface texture features 102ST, provided on one side for the first area 101 (which has no surface texture features applied thereto). In some examples, the second area may be positioned/located on either or both sides of the first area.

The first surface area may be defined as an area that experiences, in use/operation with a bearing element, high contact pressure (i.e. above a threshold - for example, for steel surfaces/contacts a threshold contact pressure value of the region of 200 MPa) with the bearing element not least due to a lubricant in that particular region under conditions of elastohydrodynamic lubrication/elastohydrodynamic lubrication regime. Such a (relatively high pressure experiencing) first area may correspond to a central region of the contact footprint, whereas a (non-central) peripheral or edge region of the contact footprint may experience relatively low pressure (i.e. below a threshold). In this regard, such a (high pressure experiencing) first area may, in effect, be smaller than and within the actual contact footprint. In some examples, such a (high pressure experiencing) area within the contact footprint is devoid of surface texture features (i.e. a central portion/band of the contact footprint is devoid of surface texture features), whereas a (relatively low pressure experiencing) non-central peripheral edge of the contact footprint may comprise surface texture features. In this regard, one may consider that the second area (which comprises surface texture features) can slightly overlap the contact footprint, i.e. overlap the edge/peripheral regions of the contact footprint, such that the edge/peripheral regions of the contact footprint comprise surface texture features. With respect to FIG. 2, this would correspond to the provision of surface texture features on an internal edge (of either or both sides) of the area 101 , with the main central portion of area 101 being devoid of surface texture features. In effect, one may consider that the contact footprint can be substantially devoid of surface texture features.

FIG. 3 shows another example of a bearing assembly 1. In this, two apparatuses 10 are provided that receive/seat a bearing element 20 therebetween. In this example, the bearing element 20 is again shown as being a rolling element bearing, namely a ball bearing.

A deformation of the bearing element 20 at its two areas of contact with the two surfaces 100 of the first and second apparatuses is schematically shown in an exaggerated manner. Each of the two apparatuses 10 may define a race (e.g. an inner race and an outer race) which one or more rolling element bearings ride on.

In the example of FIG. 3, each apparatus 10 is provided with two second areas 102_1 and 102_2 (each with its own surface texture features 102ST_1 and 102ST_2 respectively), wherein one is provided on a first side of the first area 101 (immediately adjacent thereto), and the other is provided on a second side of the first area 101 (immediately adjacent thereto).

Similar to the example of FIGs 1 and 2, in FIG. 3 the second areas 102 (and their surface texture features 102ST) are positioned/located sufficiently close/adjacent to the first area 101 such that at least a part of each of the second areas lies within the projected area 202 (and outside of the first area 101). In the example of FIG. 3, the second areas extend beyond the projected area 202 such that at least a part of each of the second areas lies outside of the projected area 202.

In the example of FIG. 3, in addition to the first area 101 and the second areas 102, each surface 100 of each apparatus 10 further comprises a third area 103. The third area 103 is adjacent to a respective second area. The third area is also devoid of surface texture features.

In other examples, surface texture features may be provided in addition to (or instead of) the provision of surface texture features to the second area. In this regard, the surface texture features may be provided further away from the first area 101 and outside of the projection area 202.

It is to be appreciated that differing types of bearing elements may be employed, for instance: a tapered rolling element bearing, a cylindrical rolling element bearing, a barrelshaped rolling element bearing, a spherical rolling element bearing, a thrust bearing, a rolling element bearing with a dub-off, and a rolling element bearing with a crowned side edge. It is to be appreciated that such differing forms and shapes of bearing elements would give rise to differing shapes and relative sizes of: instantaneous area of contact 101 , and instantaneous projection area 202, (not least for example elliptic or rectangular shapes such as may be commonly encountered in the contact mechanics and tribology); which would thus give rise to differing shapes and relative sizes of contact area 101 and projected area 202.

Various examples of the present disclosure have been described above with regards to the provision and absence of surface texture features respectively to first and second areas of a means for receiving a bearing element (e.g. a raceway). However, it is to be appreciated that, in some examples, there could be a similar provision and absence of surface texture features albeit respectively to first and second areas of a bearing element itself. In this regard, in some examples, there is provided a bearing element, for use in a bearing assembly comprising means for receiving the at least one bearing element, wherein the bearing element comprises: a first area defining an area of contact with the means for receiving the at least one bearing element, and a second area adjacent the first area; wherein the second area comprises surface texture features; and wherein the first area is substantially devoid of surface texture features.

Such provision and absence of surface texture features respectively to first and second areas of the bearing element could be in addition to or instead of provision and absence of surface texture features respectively to first and second areas of means for receiving a bearing element.

The characterization of the first and second areas, as well as the characterization of the surface texture features, as discussed with regards to FIGs. 1 to 3 could equally well apply to the first and second areas, as well as the surface texture features, of such an above- mentioned bearing element.

There now follows a discussion of tribological tests that have been performed to establish the effects of using surface texture features in bearing assemblies and the effects of the positioning of the surface texture features.

In these tests, three discs were manufactured:

1 . a first untextured disc, i.e. without surface texture features either inside or outside of a contact footprint track;

2. a second disc with surface texture features outside of a contact footprint track and no surface texture features inside the contact footprint track (this disc/testing scenario corresponds to example apparatuses and bearing assemblies in accordance with the present disclosure and discussed above); and

3. a third disc with surface texture features both inside and outside of a contact footprint track.

FIG. 4 is an image of a surface 100’ of the first disc on which no surface texture features or surface modification has been actively applied. The image is taken after the tests had been performed. The image shows a worn portion/band 101’ of the surface 100’ of the disc which is worn due to being in contact with the ball during the tests. The worn portion of the disc (including longitudinal pits caused by the wearing process and not surface texture features that have been actively/deliberately applied) thereby corresponds to an area of the disc in contact with the ball during use. Hence, the worn portion/area 101’ effectively equates to a contact footprint track /contact patch.

FIG. 5 is an image of a surface 100 of the second disc on which surface texture features 102ST has been actively applied. As with the image of FIG. 4, the image of FIG. 5 is taken after the tests had been performed. The image shows a worn portion/band 101 of the surface 100 of the disc (including longitudinal pits caused by the wearing process and not surface texture features that have been actively/deliberately applied), wherein the worn portion/area effectively equates to a first area 101 that corresponds to a contact footprint track /contact patch.

The surface texture features 102ST are provided in a second area 102 that is outside of, but in the immediate vicinity of, the first area/contact footprint track 101. No surface texture features are applied to the first area. This arrangement of surface texture features corresponds to that of the examples of the disclosure described above and shown with regards to FIGs 1 to 3.

FIG. 6 is an image of a surface 100” of the third disc on which a surface texture features 102ST have been actively applied. As with the images of FIGs 4 and 5, the image of FIG. 6 is taken after the tests had been performed. The image shows a worn portion/band 101” of the surface 100" of the disc. The worn portion/area effectively equates to a first area 101" that corresponds to a contact footprint track/contact patch.

Unlike FIG. 5, in FIG. 6, the surface texture features 101ST” are provided in the first area 101", i.e. the surface texture features are provided in the contact footprint track.

Each of the threes discs was tested in a ball on disc tribometer. The contacts were lubricated by grease. The testing was carried out under contact conditions representative of those as may be expected from typical practical applications. In this regard, the tests were performed under loads of: 0.6GPa, 0.8 GPa and 1.0 GPa; and with entrainment speeds ranging from 10 to 2,000 mm/s.

FIG. 7 shows a graph of the results of tribological tests carried out on the untextured disc 1 of FIG. 4. In such tests, the traction coefficient for disc 1 range from approximately 0.04 to 0.07.

Fl G. 8 shows a graph of the results of tribological tests carried out on disc 2 of FIG. 5, which has surface texture features outside of but in the immediate vicinity of the contact footprint track. In such tests, the traction coefficient for disc 2 range from approximately 0.04 at low entrainment speeds (10 mm/s) and approximately 0.01 at high entrainment speeds (2,000 mm/s).

Fl G. 9 shows a graph of the results of tribological tests carried out on disc 3 of FIG. 6, which has surface texture features inside the contact footprint track. In such tests, the traction coefficient for disc 3 range from approximately 0.04 up to 0.1 .

From the results shown in FIGs 7 to 9, it can be seen that the provision of surface texture features placed directly beneath the contact footprint track (i.e. as per disc 3 of FIG. 6) provides a negative effect on tribological performance and causes an increase in a measured coefficient of friction relative to the untextured disc (i.e. disc 1 of FIG. 4).

However, surprisingly, the inventors discovered that surface texture features placed outside of, but at very close proximity to, the contact footprint track on the disc, were shown to reduce the measured friction coefficient and wear simultaneously.

The positioning/location of the surface texture features of disc 3 is akin to the placement of surface texture features in certain conventional bearing assemblies, namely wherein the surface texture features are applied within a contact surface (i.e. an area of contact between one component, e.g. bearing element, and its contacting counterpart, e.g. a receiving/seating surface). Certain other conventional bearing assemblies may have surface texture features applied across an entire surface of a component, i.e. including across the contact surface. Such conventional texturing has been shown to be effective in relatively low pressure/loading conditions of contacts working under a hydrodynamic lubrication mechanism. However, as indicated above and shown in FIG. 9, such conventional texturing covering the contact surface is not effective in high pressure pressure/loading conditions of contacts working under elastohydrodynamic lubrication mechanism.

In tests, surface texture features positioned inside the contact footprint track (i.e. as per disc 3 of FIG. 6) were found not to perform well in comparison to the case where there were not any surface texture features on the disc (i.e. as per disc 1 of FIG. 4). By contrast, when the surface texture features were placed inside the projected area but just outside of the contact footprint track (i.e. as per disc 2 of FIG. 5, and as per example apparatuses in accordance with the present disclosure), they were found to produce significantly better performance in terms of reducing both friction and wear.

As will be readily appreciated, examples of apparatuses in accordance with the present disclosure are not limited to the specific dimensions and particular arrangement of surface texture features indicated in the figures of the above described tribological tests, nor the indicated operational speeds.

Examples of apparatuses in accordance with the present disclosure may provide reduced friction and/or wear in high pressure elastohydrodynamically lubricated contacts such as bearing assemblies. It has also been found that examples may perform well if a full film elastohydrodynamily lubricated contact undergoes mixed regimes of lubrication (or partial regimes of lubrication as it is sometimes is referred to in the context of tribology) and boundary regimes of lubrication.

Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation. Where a structural feature has been described, it can be replaced by means for performing one or more of the functions of the structural feature whether that function or those functions are explicitly or implicitly described.

Features described in the preceding description can be used in combinations other than the combinations explicitly described.

Although functions have been described with reference to certain features, those functions can be performable by other features whether described or not.

Although features have been described with reference to certain examples, those features can also be present in other examples whether described or not. Accordingly, features described in relation to one example/aspect of the disclosure can include any or all of the features described in relation to another example/aspect of the disclosure, and vice versa, to the extent that they are not mutually inconsistent.

Although various examples of the present disclosure have been described in the preceding paragraphs, it should be appreciated that modifications to the examples given can be made without departing from the scope of the invention as set out in the claims.

The term 'comprise' is used in this document with an inclusive not an exclusive meaning. That is any reference to X comprising Y indicates that X can comprise only one Y or can comprise more than one Y. If it is intended to use 'comprise' with an exclusive meaning then it will be made clear in the context by referring to "comprising only one ..." or by using "consisting”.

In this description, reference has been made to various examples. The description of features or functions in relation to an example indicates that those features or functions are present in that example. The use of the term 'example' or 'for example’, 'can' or 'may’ in the text denotes, whether explicitly stated or not, that such features or functions are present in at least the described example, whether described as an example or not, and that they can be, but are not necessarily, present in some or all other examples. Thus 'example’, 'for example', 'can' or 'may' refers to a particular instance in a class of examples. A property of the instance can be a property of only that instance or a property of the class or a property of a sub-class of the class that includes some but not all of the instances in the class.

In this description, references to "a/an/the” [feature, element, component, means ...] are used with an inclusive not an exclusive meaning and are to be interpreted as "at least one" [feature, element, component, means ...] unless explicitly stated otherwise. That is any reference to X comprising a/the Y indicates that X can comprise only one Y or can comprise more than one Y unless the context clearly indicates the contrary. If it is intended to use 'a’ or 'the’ with an exclusive meaning then it will be made clear in the context. In some circumstances the use of 'at least one’ or 'one or more’ can be used to emphasise an inclusive meaning but the absence of these terms should not be taken to infer any exclusive meaning. As used herein, "at least one of the following: <a list of two or more elements>" and "at least one of <a list of two or more elements>” and similar wording, where the list of two or more elements are joined by "and" or "or", mean at least any one of the elements, or at least any two or more of the elements, or at least all the elements.

The presence of a feature (or combination of features) in a claim is a reference to that feature (or combination of features) itself and also to features that achieve substantially the same technical effect (equivalent features). The equivalent features include, for example, features that are variants and achieve substantially the same result in substantially the same way. The equivalent features include, for example, features that perform substantially the same function, in substantially the same way to achieve substantially the same result.

In this description, reference has been made to various examples using adjectives or adjectival phrases to describe characteristics of the examples. Such a description of a characteristic in relation to an example indicates that the characteristic is present in some examples exactly as described and is present in other examples substantially as described.

The above description describes some examples of the present disclosure however those of ordinary skill in the art will be aware of possible alternative structures and method features which offer equivalent functionality to the specific examples of such structures and features described herein above and which for the sake of brevity and clarity have been omitted from the above description. Nonetheless, the above description should be read as implicitly including reference to such alternative structures and method features which provide equivalent functionality unless such alternative structures or method features are explicitly excluded in the above description of the examples of the present disclosure.

Whilst endeavouring in the foregoing specification to draw attention to those features of examples of the present disclosure believed to be of particular importance it should be understood that the applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

The examples of the present disclosure and the accompanying claims can be suitably combined in any manner apparent to one of ordinary skill in the art. Separate references to an "example”, "in some examples” and/or the like in the description do not necessarily refer to the same example and are also not mutually exclusive unless so stated and/or except as will be readily apparent to those skilled in the art from the description. For instance, a feature, structure, process, block, step, action, or the like described in one example may also be included in other examples, but is not necessarily included.

Each and every claim is incorporated as further disclosure into the specification and the claims are embodiment(s) of the present disclosure. Further, while the claims herein are provided as comprising specific dependencies, it is contemplated that any claims can depend from any other claims and that to the extent that any alternative embodiments can result from combining, integrating, and/or omitting features of the various claims and/or changing dependencies of claims, any such alternative embodiments and their equivalents are also within the scope of the disclosure.

Claims

CLAIMS We claim:

1. An apparatus, for use in a bearing assembly comprising at least one bearing element, the apparatus comprising: means for receiving the at least one bearing element, the receiving means comprising: a first area defining an area of contact with the bearing element, and a second area adjacent the first area; wherein the second area comprises a plurality of surface texture features; and wherein the first area is substantially devoid of surface texture features.

2. The apparatus of any previous claim, wherein the first area defines at least one of the following: a contact footprint; a contact footprint patch; a surface area of the receiving means which, during use, is contacted by the bearing element; a bearing surface; a contact footprint path; a running track; and a contact patch.

3. The apparatus of any previous claim, wherein the second area defines an area that is at least one of: non-overlapping with the first area; immediately adjacent to the first area; and located on a first and/or second side of the first area.

4. The apparatus of any previous claim, wherein the surface texture features comprises at least one of the following: one or more surface modifications; one or more protrusions; one or more recesses; one or more reservoir means for receiving and/or storing a lubricant; a coating; a solid lubricant; and a porous material.

5. The apparatus of any previous claim, wherein the second area has a different surface topography to the first area.

6. The apparatus of any previous claim, wherein the apparatus is a race for the at least one bearing element of the bearing assembly.

7. The apparatus of any previous claim, wherein the apparatus is a component in a bearing assembly configured for use in an elastohydrodynamic lubrication regime.

8. The apparatus of any previous claim, wherein the apparatus is a component in at least one of: a rolling element bearing assembly, a constant velocity joint, a gear contact, a load bearing contact, and a biological prosthetic surfaces.

9. A bearing assembly comprising: the apparatus of any previous claim; and at least one bearing element.

10. The bearing assembly of claim 9 wherein the bearing element is a rolling element bearing.

11 . The bearing assembly of claim 9 or 10, wherein the bearing assembly is a lubricated bearing assembly.

12. The bearing assembly of claim 9, 10 or 11 , wherein the bearing assembly is configured for use in an elastohydrodynamic lubrication regime.

13. The bearing assembly of any previous claims 9 to 12, wherein the bearing assembly is at least one of: a rolling element bearing assembly, a constant velocity joint, a gear contact, a load bearing contact, and a biological prosthetic surfaces.

14. A bearing element, for use in a bearing assembly comprising means for receiving the at least one bearing element, the bearing element comprising: a first area defining an area of contact with the means for receiving the at least one bearing element, and a second area adjacent the first area; wherein the second area comprises a plurality of surface texture features; and wherein the first area is substantially devoid of surface texture features.

15. A module, device or system comprising at least one of the following: the apparatus of any of previous claims 1 to 8; the bearing assembly of any of previous claims 9 to 13; and the bearing element of claim 14.