Sliding engine component

Abstract

A sliding engine component may include a sliding surface including a plastics polymer-based composite layer disposed on a substrate. The composite layer may include a matrix of plastics polymer-based material. The plastics polymer-based material may have 0.1 to 20 percent by volume of liquid-filled microcapsules distributed throughout the matrix, and incidental impurities.

Claims

1. A sliding engine component, comprising: a sliding surface including a plastics polymer-based composite layer disposed on a substrate, the composite layer including: a matrix of plastics polymer-based material including a polyimide-amide material and having distributed throughout the matrix: 0.1 to 20% volume of liquid-filled microcapsules; incidental impurities; and wherein the liquid-filled microcapsules include a shell of a polymeric material resistant to dissolution in a solvent system including at least one of a non-polar solvent and a polar aprotic solvent, wherein the shell of the liquid-filled microcapsules includes at least one of: (i) a functionalised exterior surface having at least one of a surface charge, a hydrophilic surface and a hydrophobic surface, and (ii) a coating providing a metalized exterior surface, and wherein the at least one of the functionalised exterior surface and the coating promotes suspension of the liquid-filled microcapsules within a solution of the composite layer prior to deposition of the composite layer onto the substrate.

2. A sliding engine component according to claim 1, wherein the matrix of plastics polymer-based material includes 0.5 to 5% vol. of liquid-filled microcapsules.

3. A sliding engine component according to claim 1, wherein the liquid-filled microcapsules have a mean average diameter of less than or equal to half of a thickness of the composite layer.

4. A sliding engine component according to claim 1, wherein at least one of the composite layer has a thickness of 6 m to 40 m and the liquid-filled microcapsules have a mean average diameter of 0.5 m to 10 m.

5. A sliding engine component according to claim 1, wherein the composite layer has an outer surface providing the sliding surface, and wherein at least some of the liquid-filled microcapsules are embedded in the composite layer and exposed at the outer surface.

6. A sliding engine component according to claim 1, wherein the composite layer further includes a plurality of separate sub-layers disposed one on top of the other, and wherein the plurality of sub-layers have different concentration by percent volume of the liquid-filled microcapsules.

7. A sliding engine component according to claim 6, wherein the plurality of sub-layers further include different concentrations by percent volume of a metal particulate.

8. A sliding engine component according to claim 6, wherein the plurality of sub-layers include different types of the liquid-filled microcapsules.

9. A sliding engine component according to claim 1, wherein a liquid of the liquid-filled microcapsules includes a liquid lubricant.

10. A sliding engine component according to claim 9, wherein the liquid of at least some of the liquid-filled microcapsules further includes a liquid additive different from the liquid lubricant.

11. A sliding engine component according to claim 10, wherein the liquid additive includes at least one of a corrosion inhibitor and a seal-healing additive.

12. A sliding engine component according to claim 1, wherein the polymeric material of the shell includes at least one of polyester, polyurea, and polyurethane.

13. A sliding engine component according to claim 1, wherein the composite layer further includes at least one of from 0.5 to 15% volume of a dry lubricant particulate and from 0.5 to less than 15% volume of a metal powder.

14. A sliding engine component according to claim 1, wherein the composite layer further includes from 0.1 to 5% vol. of carbon nanostructures.

15. A sliding engine component according to claim 1, wherein the matrix of plastics polymer-based material further includes a distribution of the following: from 0.5 to less than 15% vol. of a metal powder; from 0.5 to 15% vol. of a fluoropolymer particulate, the balance being the polyimide polyamide plastics polymer material apart from incidental impurities.

16. A sliding engine component according to claim 1, wherein the composite layer further includes from 0.5 to 10% vol. of an inorganic particulate.

17. A sliding engine component according to claim 1, wherein the substrate includes a metallic backing material layer and the composite layer is disposed on the metallic backing material layer.

18. A sliding engine component according to claim 1, wherein the substrate includes a metallic backing layer and a metallic lining layer and the composite layer is disposed on the metallic lining layer.

19. A sliding engine component according to claim 1, wherein the substrate includes a non-sputter-coated metallic base layer and the composite layer is bonded to the non-sputter-coated metallic base layer via a sputter-coated Al-based intermediate layer.

20. A sliding engine component according to claim 1, wherein the sliding engine component is a sliding bearing assembly component selected from at least one of: a bearing lining shell, a bushing, a bearing surface of a crankshaft, a bearing surface of a camshaft, a bearing surface of a connecting rod, a thrust washer, a bearing surface of a bearing block, and a bearing surface of a bearing cap.

21. A sliding engine component according to claim 1, wherein the sliding engine component is a piston assembly component selected from at least one of a piston ring, a piston skirt, and a cylinder wall.

22. A sliding engine component according to claim 9, wherein the liquid lubricant has a viscosity of 5.6 cSt.

23. A method of manufacturing a sliding engine component, comprising: providing a solvent, wherein the solvent includes at least one of a non-polar solvent and a polar aprotic solvent; adding a plastics polymer-based resin material and liquid-filled microcapsules to the solvent and intermixing the plastics polymer-based resin material and liquid-filled microcapsules to provide a solvent mixture, wherein the liquid-filled microcapsules include a shell of a polymeric material resistant to dissolution in the solvent; coating the solvent mixture onto a substrate to provide a plastics polymer-based composite layer on the substrate composed of a plastics polymer-based material matrix including from 0.1 to 20 percent volume of the liquid-filled microcapsules and incidental impurities distributed throughout the plastics polymer-based material matrix; and treating the solvent mixture so as to remove the solvent and consolidate the plastics polymer-based material matrix.

24. A method according to claim 23, wherein the plastics polymer-based resin material includes a polyimide-amide resin and the solvent includes at least one of n-ethyl-2-pyrrolidone, n-methyl-2-pyrrolidone, and xylene; and further including maintaining the liquid-filled microcapsules in suspension within the solvent mixture prior to coating the solvent mixture onto the substrate.

25. A method according to claim 23, wherein coating the solvent mixture onto the substrate to provide the plastics polymer-based composite layer includes depositing at least two sub-layers overlaying the substrate one on top of the other and providing the at least two sub-layers with different concentrations by percent volume of the liquid-filled microcapsules.

26. A method according to claim 23, further comprising providing the shell of the liquid-filled microcapsules with a functionalised exterior surface to promote suspension of the liquid-filled microcapsules in the solvent mixture prior to coating the solvent mixture onto the substrate, the functionalised exterior surface including an anionic or cationic surface charge common to all of the liquid-filled microcapsules.

27. A sliding engine component according to claim 26, wherein the second sub-layer includes a higher concentration of the liquid-filled microcapsules by percent volume than the first sub-layer, and wherein the liquid-filled microcapsules of the second sub-layer include a first type of microcapsules filled with a liquid lubricant and a second type of microcapsules filled with a liquid lubricant and an additive.

28. A sliding engine component according to claim 26, wherein the plastic polymer-based material matrix further includes a metal particulate distributed throughout the first sub-layer and the second sub-layer; and wherein the second sub-layer has a lower concentration by percent volume of the liquid-filled microcapsules than the first sub-layer, and the second sub-layer has a higher concentration by percent volume of the metal particulate than the first sub-layer.

29. A sliding engine component, comprising: a plastics polymer-based composite layer disposed on a metallic substrate, the plastics polymer-based composite layer composed of a plastics polymer-based material matrix including from 0.1 to 20% volume of liquid-filled microcapsules distributed throughout the plastics polymer-based material matrix and incidental impurities; wherein the plastics polymer-based composite layer includes a first sub-layer and a second sub-layer overlaying the metallic substrate one on top of the other, the second sub-layer disposed between the metallic substrate and the first sub-layer; and wherein the liquid-filled microcapsules are embedded throughout the first sub-layer and the second sub-layer of the plastics polymer-based composite layer, and the first sub-layer has a different concentration by percent volume of the liquid-filled microcapsules than the second sub-layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

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

(2) FIG. 1A shows a schematic perspective view of a semi-cylindrical bearing shell;

(3) FIG. 1B shows a schematic cross-sectional view through part of a bearing shell of FIG. 1A;

(4) FIG. 1C shows a schematic cross-sectional view through part of a bearing shell comprising two different composite sub-layers;

(5) FIG. 1D shows a schematic cross-sectional view through part of a bearing shell comprising a further two different composite sub-layers;

(6) FIG. 2A shows a cut-away view of a piston within a piston cylinder; and

(7) FIG. 2B shows a perspective view of the piston of FIG. 2A.

DETAILED DESCRIPTION

(8) In the described embodiments, like features have been identified with like numerals.

(9) FIG. 1A schematically illustrates a sliding bearing 100 (e.g. a sliding engine component) in the form of a hollow semi-cylindrical bearing lining shell (commonly referred to as a half bearing). FIG. 1B shows a cross-sectional view through the sliding bearing 100 of FIG. 1A.

(10) The half bearing 100 comprises: a substrate comprising a strong steel backing 102, a copper-based bearing lining layer 104 on the concave inner surface of the backing; and, a plastics polymer-based composite overlay layer 106 comprising liquid filled microcapsules 108 that is provided directly onto the lining layer (i.e. the substrate).

(11) The adhesion of the composite overlay layer 106 may be enhanced by the application of a surface preparation technique to the surface of the bearing lining layer 104, such as grit-blasting, prior to deposition of the composite overlay layer. Alternatively, an additional aluminium-based sputtered layer (not shown) may be provided directly onto the lining layer 104, before the composite overlay layer 106.

(12) The overlay layer 106 is configured to provide a running surface over the lifetime of the sliding bearing 100 (e.g. over engine-life), in contrast to a less robust running-in layer for short-term use, for running-in at the start of life. The overlay layer 106 is the innermost layer of the half bearing, which is configured to face a moving element in a bearing assembly (e.g. the overlay layer receives a journaled shaft in an assembled bearing, which mutually cooperate, with an intervening oil film).

(13) The composite overlay layer 106 comprises a matrix of plastics polymer-based composite material having liquid-filled microcapsules distributed throughout the matrix. The composite layer comprises 2% vol liquid-filled microcapsules, 12.5% vol Al powder, 5.7% vol PTFE particulate, 4.8% vol silane powder, <0.1% vol other components, and balance polyimide/amide plastics polymer, apart from incidental impurities.

(14) The polyimide/amide based material is applied as a mixture with a solvent. A suitable solvent may comprise n-methyl-2-pyrrolidone xylene and can be employed in various proportions in order to achieve a particular desired viscosity of mixture suitable for coating onto the substrate. Note that in the specification, above, of the composition of the plastics polymer-based composite overlay layer 106 is that which remains after the overlay layer has been fully cured (e.g. the solvent has been substantially removed).

(15) A mixture is formed with the polyimide/amide in the solvent, the microcapsules and other components. The mixture may be agitated to maintain the components in suspension, prior to coating the bearing substrate. The composite overlay layer 106 is built up by a spray coating process in which repeated deposition of thin spray coatings is interspersed with flash off phases to remove solvent. After the final coating deposition step, the sliding bearing is given a final cure at 150 to 250 C. for about 30 minutes, to consolidate the plastic polymer-based matrix.

(16) Alternatively, the plastics polymer-based composite layer 106 could be deposited by a screen printing (i.e. through a mask), a pad printing process (i.e. an indirect offset printing process, e.g. in which a silicone pad transfers a patterned layer of the plastics polymer composite material onto the sliding bearing substrate), or by a transfer rolling process.

(17) Desirably the solvent mixture is of a suitable viscosity that the coating technique of applying the solvent mixture to the substrate results in the final thickness of the plastics polymer-based composite layer being at a desired thickness without the need to machine to a desired final wall, thickness. However, machining of the plastic polymer-based composite layer may be undertaken if required.

(18) In the alternative case that an interlayer is additionally provided, the interlayer is deposited by a sputter coating process, has a thickness of 2 to 3 m, and is strongly adhered to the bearing lining layer 104. The interlayer may comprise 1.5% wt Mn with the remaining balance to 100% wt of Al, apart from incidental impurities. (In alternatives: the interlayer may comprise 6% wt Sn, 1% Cu, 1% wt Ni, and 2% wt Si, with the balance to 100% wt being Al apart from incidental impurities; or the interlayer may comprise pure Al, apart from incidental impurities.)

(19) The microcapsules 108 comprise a shell 108A filled with liquid 108B. The liquid 108B within the shell 108B is preferably a liquid lubricant and may comprise other oil additives. The shell comprises a polymeric material (e.g. polyester, polyuria, polyurethane, cellulose, polyethylene, polypropylene, polystyrene), having a coating or functionalised surface that promotes suspension of the microcapsules within the solution of the composite layer before it is deposited onto the substrate. The microcapsules 108 are embedded throughout the composite layer 106, and at the surface 110 of the composite layer, the microcapsules are exposed. The composite layer 106 has a thickness T1 and the embedded liquid-filled microcapsules 108 have a diameter T2, which is no more than half the thickness of the composite layer.

(20) FIG. 18 schematically illustrates a separate cooperating component 112 (i.e. a tribological partner, e.g. part of a crankshaft) that is moving in the direction of the arrow A relative to the sliding bearing. FIG. 1B illustrates the situation in which component 112 contacts the surface 110 of the sliding bearing. During contact, the component 112 abrasively wears the surface 110 of the sliding bearing 100, exposing microcapsules 108, which are broken open, leading to the release of further liquid lubricant 1088 out of the shells 108A. The released liquid 108B provides localised, emergency lubrication between the component 112 and the surface 110 where they are in contact, reducing the risk of seizure (i.e. localised micro-welding) occurring between the component and the sliding bearing 100.

(21) FIG. 1C schematically illustrates a cross-sectional view through the sliding bearing 100, that differs from the sliding bearing 100 of FIGS. 1A and 1B by the composite layer comprising two different sub-layers 106A and 106B. The lower sub-layer 106A, adjacent the substrate (i.e. adjacent the bearing lining layer 104), has a higher concentration of microcapsules 108 than the upper sub-layer 106B. The upper sub-layer 106B and the lower sub-layer 106A both comprises a microcapsules 108-1 of a first type (e.g. filled with a liquid lubricant), and the lower sub-layer 106A additionally comprises microcapsules 108-2 of a second type (e.g. filled with lubricant and a self-healing additive). If the upper sub-layer 106B should become worn through, the lower sub-layer 106A would become exposed, and the higher concentration of microcapsules may provide an enhanced level of lubrication and seizure resistance. Further, if a crack should penetrate into the lower sub-layer 106A, self-healing additive may be released to seal the crack, to prevent corrosive lubricating oil in the bearing clearance from penetrating through the crack to the bearing lining layer 104 of the substrate.

(22) FIG. 1D schematically illustrates a cross-sectional view through the sliding bearing 100, that differs from the sliding bearing 100 of FIGS. 1A and 1B by the composite layer comprising two different sub-layers 106A and 106B. Both sub-layers 106A and 106B contain both microcapsules 108 and metal particulate 112 (e.g. aluminium flakes). The lower sub-layer 106A has a lower concentration of microcapsules 108 than the upper sub-layer 106B. The lower sub-layer 106A has a higher concentration of metal particulate 112 than the upper sub-layer 106B. If the upper sub-layer 106B should become worn through, the lower sub-layer 106A would become exposed, and the higher concentration of metal particulate may provide an enhanced level of wear resistance.

(23) Although the illustrated sliding bearing is a semi-cylindrical bearing shell, the present invention may also be applied to other sliding bearings, including thrust washers, tubular bushing, a bearing surface of a connecting rod, a shaft configured for journaling in a bearing, a bearing block, and a bearing cap.

(24) Although illustrated in the case of a pre-formed bearing shell, it will be appreciated that the present invention also applies to blanks from which sliding bearings may be formed, e.g. flat strip or sheet materials from which such sliding bearings may then be formed after the coating step.

(25) The present invention also relates to piston assembly components, e.g. piston rings, piston skirts, or the cylinder wall of the engine block. FIG. 2A illustrates a piston assembly 220 comprising sliding engine components, and FIG. 2B illustrates the corresponding piston 222.

(26) The piston assembly 220 is adapted for reciprocal movement of a piston 222 within a cylinder 224 of an internal combustion engine 226. The piston 222 comprises a body 228 having a crown 230 formed at the uppermost margins of the body 228 and a skirt 232 depending from the crown 230. The piston 222 further includes ring lands 234 extending about the circumference of the body 228 and adapted to retain piston rings 236. A pin bore 238 extends through the lower margins of the body 228 and is adapted to receive a piston pin 240.

(27) The piston skirt 232 includes an outer circumference having a major thrust side 242 and a minor thrust side 244 formed substantially opposite each other on the outer circumference of the skirt. The piston 222, and more particularly the skirt 232, is adapted for relative sliding motion with respect to the wall of a cylinder 246.

(28) A connecting rod 248 is adapted to interconnect the piston 222 and a crankshaft (not shown, but generally known in the art). The connecting rod 248 is fastened to the crankshaft using bolts 250. The connecting rod 248 also includes a bore 252 at the opposite end (which may be lined with a plain bush sliding bearing). A piston pin 240 is operatively received through the alignment pin bore 238 in the piston 222 and the bore 252, extending through the connecting rod 248.

(29) In use, fuel is combusted within the cylinders 224, causing reciprocation of the pistons 222.

(30) The piston 222 drives the connecting rod 248, which drives the crankshaft, causing it to rotate relative to bearings supported by the engine 226. In this way, power may be translated from the piston, via the crankshaft, to drive a vehicle or other device. Specifically, the combustion pressure within the cylinder 224 drives the piston 222 downward in a substantially linear motion. However, in addition to the substantially linear motion of the piston 222, there is some lateral movement due to the gap (i.e. tolerance) between the outer surface of the piston skirt 232 and the interior wall 246 of the cylinder 224.

(31) As a result of lateral movement by the piston 222 within the cylinder 224, the piston skirt 232 presses against the cylinder wall 246 during the powerstroke and return movements. The surface areas of the piston 222 that may contact the cylinder wall 246 during major and minor thrust movements are the major thrust side 242 and the minor thrust side 244. While lubricating oil generally prevents metal-to-metal contact between the piston skirt 232 and the cylinder wall 246, factors such a load, temperature and insufficient lubrication may reduce or eliminate the layer of lubricant and cause scuffing on the surface of the piston skirt 232 and/or the cylinder wall 246. Scuffing in this area can eventually cause the engine 226 to seize or fail.

(32) Accordingly, it is important to keep the major thrust side 242 and the minor thrust side 244 of a piston skirt 232 lubricated. To this end, the piston 222 of the present invention includes a coating 206 provided on the piston skirt 232 so as to be juxtaposed between the skirt 232 and the cylinder 224 to improve lubrication between the piston 222 and a cylinder 224. Although FIGS. 2A and 2B illustrate an arrangement in which the coating 206 on the piston skirt 232 is not patterned, other arrangements of the coating may be provided in which the coating is patterned, e.g. with grooves separating the coating into islands of coating on the skirt.

(33) Similarly, a lubrication coating 206 may be provided on at least the outer circumferential surface of the piston rings 236 (e.g. the coating 206 of the present invention may be provided on the two piston rings closest to the pin bore 238; the piston ring closest to the crown of the piston may have an inorganic ceramic coating). Although not illustrated, the cylinder wall (or cylinder liner, in the case of a lined/sleeved piston cylinder) and bearing surfaces of the connecting rod 248, may also be provided with a coating according to the present invention. These lubrication coatings 206 and 206 are plastics polymer-based composite layers comprising liquid-filled microcapsules 208 and 208, in accordance with the present invention.

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

(35) 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.

(36) 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.

(37) 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.