Thrust washer

Abstract

A thrust washer for a sliding bearing may include a thrust washer substrate having an axial face. The thrust washer may also have a polymer layer of profiled thickness on the axial face of the substrate. The profiled polymer layer may be provided with at least one oil distribution groove.

Claims

1. A thrust washer for a sliding bearing, comprising: a thrust washer substrate having an axial face, and a polymer layer of profiled thickness on the axial face of the substrate, wherein the profiled polymer layer is provided with at least one oil distribution groove, and includes a stacked plurality of polymer sub-layers.

2. The thrust washer according to claim 1, wherein the polymer sub-layers are differently patterned.

3. The thrust washer according to claim 1, wherein the at least one oil distribution groove extends only part way through the profiled polymer layer.

4. The thrust washer according to claim 1, wherein the at least one oil distribution groove extends through the profiled polymer layer, and the profiled polymer layer comprises a plurality of disconnected portions, separated by the at least one oil distribution groove.

5. The thrust washer according to claim 4, wherein the at least one oil distribution groove extends into the thrust washer substrate.

6. The thrust washer according to claim 1, wherein the at least one oil distribution groove comprises a channel and at least one ramp region.

7. The thrust washer according to claim 6, wherein the ramp region is provided in the profiled polymer layer, and the thickness of the profiled polymer layer in the at least one ramp region increases away from the channel.

8. The thrust washer according to claim 7, wherein the at least one ramp region has a ramp slope in which the increase in thickness of the polymer is less than 25 m per 1 mm across the axial face, perpendicular to the at least one oil distribution groove.

9. The thrust washer according to claim 7, wherein the at least one oil distribution groove comprises a channel between a first ramp region and a second ramp region.

10. The thrust washer according to claim 6, wherein the at least one oil distribution groove comprises a channel between a first ramp region and a second ramp region.

11. The thrust washer according to claim 6, wherein the profiled polymer layer is provided with at least one pad region of uniform thickness adjacent the at least one oil distribution groove.

12. The thrust washer according to claim 1, wherein the plurality of polymer sub-layers comprises sub-layers of different thicknesses.

13. A flange bearing comprising a bearing shell and a thrust washer provided at an axial end of the bearing shell, the thrust washer including: a thrust washer substrate having an axial face, and a polymer layer of profiled thickness on the axial face of the substrate, wherein the profiled polymer layer is provided with at least one oil distribution groove and with at least one pad region of uniform thickness adjacent the at least one oil distribution groove.

14. A method of manufacturing a thrust washer for a sliding bearing, the thrust washer having a thrust washer substrate having an axial face and a profiled polymer layer on the axial face of the substrate, the profiled polymer layer being provided with at least one oil distribution groove, the method comprising: forming the profiled polymer layer on the axial face of the substrate, and curing the profiled polymer layer; wherein the profiled polymer layer is formed by depositing a plurality of polymer sub-layers.

15. The method according to claim 14, wherein the profiled polymer layer is formed by at least one of a spraying process and a printing process.

16. The method according to claim 15, wherein successive polymer sub-layers are differently patterned, to build up a profiled polymer layer of non-uniform thickness.

17. The method according to claim 14, wherein the plurality of polymer sub-layers comprises sub-layers of different thicknesses.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the invention are further described hereinafter with reference to the accompanying drawings, in which:

(2) FIGS. 1A and 1B show perspective views of thrust washers according to the present invention; and

(3) FIG. 2A shows a cross-sectional view of a thrust washer according to a first embodiment the present invention, formed by a first manufacturing method;

(4) FIGS. 2B and 2C show cross-sectional views of a thrust washer according to the first embodiment the present invention, formed by a second manufacturing method, and shown at different stages of manufacture before and after a prolonged curing stage;

(5) FIGS. 3A and 3B show cross-sectional views of thrust washers according to a second embodiment the present invention, formed by two different manufacturing methods;

(6) FIG. 4A shows a cross-sectional view of a thrust washer according to a third embodiment the present invention;

(7) FIGS. 4B and 4C show cross-sectional views of alternative thrust washers according to the third embodiment of the present invention;

(8) FIG. 5A shows a cross-sectional view of a thrust washer according to a fourth embodiment of the present invention;

(9) FIG. 5B shows a cross-sectional view of a thrust washer according to a fifth embodiment of the present invention; and

(10) FIG. 6 shows a cross-sectional view through a thrust washer according to a sixth embodiment of the present invention.

DETAILED DESCRIPTION

(11) In the described embodiments, like features have been identified with like numerals, albeit in some cases having one or more of: increments of integer multiples of 100; and, typographical marks (e.g. primes). For example, in different figures, 100, 100, 200, 200, 300, 300, 400, 400 and 400, 500, 500 and 600 have been used to indicate a thrust washer.

(12) FIG. 1A illustrates a thrust washer 100 that has a substantially semi-annular shape (e.g. it may have projecting hooks and tabs, and tapers from a generally semi-annular shape, for engagement with other parts of the bearing assembly). An axial face 102 (i.e. a face perpendicular to the axis of rotation of a shaft received into a bearing assembly comprising the thrust washer) of the thrust washer 100 has parallel oil distribution grooves 104 running between the inner and outer edges of the thrust washer. In use, lubricating oil is pumped into the bearing clearance between the corresponding bearing shell and rotating crankshaft journal, and leaks out into the further clearance between the thrust washer and the counterface of the rotating crankshaft web. The provision of the oil distribution grooves 104 in the axial face 102 of the thrust washer 100 enhances the quality of the oil film between the thrust washer and the shaft.

(13) FIG. 1B illustrates an alternative arrangement of oil distribution grooves 104 on the axial face 102 of a further thrust washer 100, in which the oil distribution grooves are aligned radially on the axial face.

(14) FIG. 2A illustrates a cross-sectional view through part of such a thrust washer 200, viewed perpendicular to the oil distribution grooves 204. The thrust washer 200 comprises a metal substrate (e.g. a steel backing) 206 and a profiled polymer layer 208 on an axial face of the substrate.

(15) The polymer layer 208 is profiled to provide oil distribution grooves 204 between pad regions 210 of uniform thickness. The oil distribution grooves 204 each comprise a channel 204A and ramp regions 204B between the channel and the neighbouring pad regions 210. In the illustrated example, the ramp regions 204B have a low ramp slope of approximately 1:300 to 1:100, e.g. 1:200, corresponding to approximately .

(16) The profiled polymer layer 208 in FIG. 2A is formed by a printing deposition process or a spray deposition process. The maximal thickness of the polymer layer 208 (which is in the pad regions 210) is 20 to 100 m, once fully cured.

(17) FIG. 2B illustrates a corresponding thrust washer 200, prior to a prolonged final curing stage, in which the profiled polymer layer 208 is instead formed by a multi-layered deposition process, in which successive polymer sub-layers 212 that are deposited on the substrate 206 have different patterns (e.g. successive layers may be narrower), that build-up to form the profiled polymer layer 208. Multi-layer deposition enables accurate control of the thickness of the profiled polymer layer 208. Between deposition of successive sublayers 212, each sub-layer is dried to remove solvent (known as flash-curing), and after deposition of the final sub-layer, the assembled profiled polymer layer 208 is cured by prolonged heating to set the polymer (e.g. inducing cross-linking).

(18) Curing the polymer smoothes the profile of the profiled polymer layer 208, and the polymer may comprise a levelling agent, which further promotes smoothing of the profile. FIG. 2C shows the thrust washer after it has been cured.

(19) FIG. 2B shows the profiled polymer layer 208 built-up by only a small number of polymer sub-layers 212 (e.g. 1 to 25 m thick sub-layers). However, to promote evaporation of the solvent after the deposition of each sub-layer, a larger number of thinner polymer layers 212 may be used. Further, the use of thinner sub-layers enables the profiled polymer layer to be formed with greater accuracy. For example, each polymer sub-layer 212 may be no more than 2 m thick, and the thickness of the profiled polymer layer 208 in the ramp region 204A and 204B may increase by 20 m to 55 m, over a length (parallel to the substrate 206) of several millimeters.

(20) Suitable processes by which polymer layers 212 may be deposited include spraying, screen printing and pad printing. In particular, screen printing or pad printing may be used to deposit patterned polymer layers, e.g. one or more layers of uniform thickness.

(21) The oil distribution grooves 204 in FIG. 2A extend through the profiled polymer layer 208 to expose regions 214 of the substrate 206. In contrast, the profiled polymer layer 308 may extend across the substrate without a break, as illustrated in FIGS. 3A and 3B. Advantageously, in such thrust washers 300 and 300, a barrier of polymer material is provided between the substrate 306 and the lubricating oil, in use, preventing corrosion of the substrate 306 and 306 by additives in the lubricating oil.

(22) FIG. 4A illustrates a third embodiment in which the oil distribution grooves 404 extend through the profiled polymer layer 408 into the substrate 406. In particular, the channel 404A may be provided recessed into the substrate 406, whilst the ramp regions 404B are provided in the profiled polymer layer 408. Such an arrangement may be more easily manufactured, by machining or embossing the channel 404A into the substrate 406, and forming the ramp regions 404B by profiling the polymer layer 408. Formation of the channel 404A has wider tolerances than the formation of the ramp regions 404B, and advantageously, forming the channel in the substrate enables it to be more quickly formed. Further, forming only the ramp regions 404B in the profiled polymer layer 408, requires a thinner polymer, which can be more quickly manufactured and with greater accuracy.

(23) FIG. 4B illustrates an alternative design of the third embodiment, formed by the multi-layer deposition process. Advantageously, for the multi-layer deposition process, forming only the ramp regions 404 B.sub.1 and 404B.sub.2 in the profiled polymer 408 enables the thrust washer 400 to be formed more quickly as it requires deposition and curing of fewer polymer layers 412.

(24) In FIGS. 2A to 4A each oil distribution groove is substantially symmetric, having a channel formed between a pair of ramp regions having equal ramp slopes. However, the thrust washer may be optimised for rotation of the shaft in a particular direction, in which case the ramp regions may have different ramp slopes (i.e. the oil distribution grooves may have asymmetric cross-sections), or one of the ramp regions may be omitted. Accordingly, FIG. 4B illustrates a thrust washer 400 having ramp regions 404 B.sub.1 and 404B.sub.2 having different ramp slopes .sub.1 and .sub.2.

(25) Similarly, FIG. 4C illustrates a thrust washer 400 in which the oil distribution groove has only one ramp region 404B, with a relatively abrupt edge 416 (e.g. providing an edge that is perpendicular to the plane of the thrust washer, or at more than 45 to the plane of the thrust washer) to the polymer 408 on the other side of the channel 404A.

(26) In FIGS. 2A to 4C, each oil distribution groove has comprises a channel and at least one ramp region. However, as illustrated in the embodiment of FIG. 5A, the thrust washer 500 may comprise oil distribution grooves without ramp regions, in which the grooves each comprise channels 504A, which are defined by abrupt edges 516A and 516B (e.g. providing an edge that is perpendicular to the plane of the thrust washer, or that is at an angle of more than 45 to the plane of the thrust washer) through the profiled polymer 508 to a recessed channel 518 formed in the substrate 506. Alternatively, the oil distribution grooves may extend only to the surface of the substrate, like the grooves 204A in FIG. 2A, or may be less deep than the maximum thickness of the polymer, like the grooves 304A in FIG. 3A.

(27) FIG. 5A shows such an embodiment in which the abrupt edges 516A and 516B are substantially perpendicular to the plane of the thrust washer, before the polymer sub-layers 512 have undergone a prolonged cure. In depositing polymer sub-layers 512 having the same pattern (e.g. where there is no requirement for a stepped ramp region to smooth during curing), the profiled polymer layer 508 may be deposited in thicker sub-layers, e.g. up to 25 m thick, enabling more rapid deposition, with lower manufacturing cost. FIG. 5B shows a similar embodiment, 500, after the sub-layers have undergone a prolonged cure, and which differs from the embodiment of FIG. 5A by the abrupt edges 516A and 516B of the polymer layer 508 having an edge that is at an angle of more than 45 to the plane of the thrust washer (e.g. 65).

(28) The sub-layers 612A and 612B of the profiled polymer layer may have different thicknesses and physical properties, as illustrated in FIG. 6. For example, the sub-layers 612B further from the substrate 606, may be thicker than the sub-layers 612A adjacent the substrate.

(29) In the illustrated examples: The metal substrate is a steel substrate. The profiled polymer layer is a composite of a plastics polymer matrix and particulate distributed throughout the matrix. The plastics polymer material is selected from the group consisting of: polyimide/amide resin, acrylate resin, epoxy resin, fluoropolymer and formaldehyde. In particular, the polymer may be a composite polyimide/amide based polymer, such as a composite having a matrix of a polyimide/amide plastics polymer material and having distributed throughout the matrix: from 5 to less than 25% vol of a metal particulate (e.g. metal powder and/or metal flakes); from 1 to 20% vol of a fluoropolymer, the balance being the polyimide/amide resin apart from incidental impurities. Further, the polymer composite may be 12.5% vol Al, 5.7% vol PTFE particulate, 4.8% vol silane, <0.1% vol other components, and balance (approximately 77% vol) polyimide/amide.

(30) Although illustrated in FIGS. 1A and 1B in relation to a generally semi-annular thrust washer, the present invention equally applies to annular or circular thrust washers.

(31) The figures provided herein are schematic and not to scale.

(32) Throughout the description and claims of this specification, the words comprise and contain and variations of them mean including but not limited to, and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

(33) Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

(34) The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.