SLIDING ELEMENT COMPRISING POLYMER OVERLAY

Abstract

A bearing element may include an overlay layer which forms a bearing surface against a steel journal or the like. The overlay layer may be formed from a bearing material comprising a polymer matrix of polyamide-imide polymer material, melamine cyanurate particulate, and metal oxide particulate. A method of forming the bearing element comprising the bearing material are also provided.

Claims

1. A bearing material, comprising: a polymer matrix of polyamide-imide polymer material; melamine cyanurate particulate; metal oxide particulate; and at least 25 wt % metallic particulate dispersed within the polymer matrix.

2. The bearing material according to claim 1, wherein the metallic particulate comprises aluminium flakes.

3. The bearing material according to claim 1, wherein the metal oxide particulate comprises one or more of cerium oxide, tin oxide, titanium dioxide, and zirconium dioxide.

4. The bearing material according to claim 1, including between approximately 5 wt % and 12 wt % melamine cyanurate particulate.

5. The bearing material according to claim 1, including between approximately 3 wt % and 9 wt % metal oxide particulate.

6. The bearing material according to claim 1, including between approximately 29 wt % and 38 wt % metallic particulate.

7. The bearing material according to claim 1, further comprising at least one of a dispersant, an adhesion agent, and a leveler.

8. The bearing material according to claim 1, wherein the metal oxide particulate has an average particle size of between approximately 0.1 μm and 2.0 μm.

9. The bearing material according to claim 1, wherein the metal oxide particulate comprises cerium oxide, and the metallic particulate comprises aluminium flakes, and wherein the bearing material comprises between approximately 5 wt % and 12 wt % melamine cyanurate particulate, between approximately 3 wt % and 9 wt % metal oxide particulate, and between approximately 29 wt % and 38 wt % metallic particulate.

10. A bearing element, comprising: a substrate; and an overlay layer on the substrate; wherein the overlay layer comprises a bearing material according to claim 1.

11. The bearing element according to claim 10, wherein the bearing material is provided as an overlay layer, and wherein the overlay layer includes a thickness of between approximately 3 μm and 18 μm.

12. The bearing element according to claim 10, further comprising an intermediate layer between the substrate and the overlay layer.

13. The bearing element according to claim 12, wherein the intermediate layer comprises at least one of a copper-based material, and an aluminium-based material.

14. A method of forming an overlay layer of bearing material on a substrate, the method comprising: mixing polyamide-imide polymer material with melamine cyanurate particulate, metal oxide particulate, metallic particulate, and at least one solvent to form a pre-formulation; applying the pre-formulation to a substrate; and curing the pre-formulation to form an overlay layer of bearing material; wherein the overlay layer of bearing material comprises at least 25 wt % metallic particulate.

15. The method according to claim 14, wherein applying the pre-formulation to the substrate comprises at least one of spraying and screen printing.

16. The bearing element according to claim 10, wherein the metallic particulate of the bearing material comprises aluminium flakes.

17. The bearing element according to claim 10, wherein the metal oxide particulate of the bearing material comprises one or more of cerium oxide, tin oxide, titanium dioxide, and zirconium dioxide.

18. The bearing element according to claim 10, wherein the bearing material includes between approximately 5 wt % and 12 wt % melamine cyanurate particulate.

19. The bearing element according to claim 10, wherein the bearing material includes between approximately 3 wt % and 9 wt % metal oxide particulate.

20. The bearing element according to claim 10, wherein the bearing material includes between approximately 29 wt % and 38 wt % metallic particulate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0103] The invention will further be described by way of example only with reference to the accompanying drawing, in which:

[0104] FIG. 1 shows a perspective view of a bearing element according to preferred embodiments of the present invention.

[0105] FIG. 2 is a graph showing volume loss of material (wear) in tests of two different overlays, including one overlay embodying the invention.

DETAILED DESCRIPTION

[0106] FIG. 1 schematically illustrates a bearing element, the bearing element is a semi-cylindrical bearing shell 100, which is also commonly referred to as a half bearing or a half shell, for a main bearing assembly of an internal combustion engine for retaining a cylindrical journal of a crankshaft.

[0107] The bearing shell 100 has a layered construction incorporating a substrate comprising a steel substrate 102 and intermediate or lining layer 104 comprising a layer of copper-tin bronze material. An overlay 106 of a bearing material is disposed on top of the intermediate layer 104.

[0108] Overlay layer 106 is formed from a bearing material comprising a polymer matrix of polyamide-imide polymer material with melamine cyanurate particulate, metal oxide particulate, and metallic particulate dispersed within the polymeric matrix.

[0109] The bearing material comprises about 9 wt % melamine cyanurate particulate.

[0110] The melamine cyanurate particulate has an average particle size of between about 2 μm and about 5 μm.

[0111] The metal oxide is cerium oxide and the bearing material comprises about 6 wt % cerium oxide particulate. The cerium oxide particulate has an average particle size of about 1 μm.

[0112] The metallic particulate comprises aluminium flakes, and the bearing material comprises about 35 wt % aluminium flakes. The aluminium flakes have a length of less than 10 μm in a longest dimension and less than 1 μm in a dimension perpendicular to a longest dimension.

[0113] The melamine cyanurate particulate, metal oxide particulate, and metallic particulate are distributed substantially homogeneously throughout the polymer matrix.

[0114] The bearing material also comprises a dispersant and a leveller, the relative quantities of which are set out below.

[0115] An adhesion agent is also added to the pre-formulation shortly before the pre-formulation is applied to the intermediate layer.

[0116] The overlay layer comprising the bearing material has a thickness of about 10 μm.

[0117] The bearing element shown in FIG. 1 is formed by the following method.

[0118] Polyamide-imide polymer material is mixed with melamine cyanurate particulate, cerium oxide particulate, aluminium flakes, a dispersant, and a leveller. A solvent is added to the mixture to form a pre-formulation which is capable of being applied to a substrate. The solvent comprises a mixture of n-butyl acetate and n-ethyl pyrrolidone.

[0119] The relative quantities, given in weight percentages, of the components of the finished bearing material, following the drying and curing steps, are set out below in Table 1.

TABLE-US-00001 TABLE 1 wt % in Bearing Component Material Polyamide-imide Balance Aluminium flakes 29 to 38 Melamine cyanurate particulate  5 to 12 Cerium oxide particulate 3 to 9 Levellers and Dispersants 0.5 to 5.sup.  Adhesion agent 3 to 6

[0120] The method further comprises providing a steel substrate 102 having an intermediate layer 104 provided on its surface. The pre-formulation is then applied to the intermediate layer using spraying. The applied pre-formulation is then dried to remove the solvent. The dried pre-formulation is then cured using a thermal curing process at a temperature and for a duration to achieve a desired degree of cross-linking of the polyamide-imide polymer matrix. The pre-formulation is cured to form an overlay layer of bearing material having the composition set out in Table 1.

[0121] The volume loss of material, measured in mm.sup.3, is a measurement of overlay wear.

[0122] Two groups of bearing samples were tested under the same wear conditions, termed Group A and Group B.

[0123] Group A included six bearing samples according to the prior art and was used as a control group. Each bearing sample of Group A included a PAI-based overlay according to the prior art. The overlay on the bearings of Group A did not include between 29 wt % and 38 wt % aluminium flakes, or any melamine cyanurate particulate.

[0124] Group B included six bearing samples according to the present invention. Each bearing sample of Group B included an overlay having the composition set out in Table 1.

[0125] The spread of volume loss of the samples in Group A and Group B are shown in FIG. 2. The bearings of Group A exhibited a volume loss of between 4.8 mm.sup.3 and 5.2 mm.sup.3, whereas the bearings of Group B exhibited significantly less volume loss, between 3.4 mm.sup.3 and 3.7 mm.sup.3.

[0126] Accordingly, it was shown that bearings including a bearing material according to the present invention exhibit superior wear resistance compared to those of the prior art.

[0127] Although described herein and illustrated in the drawing in relation to a half bearing shell, the present invention may equally apply to other sliding engine components, including semi-annular, annular or circular thrust washers, and bushes, and engines comprising such sliding engine component.