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EP-4198327-B1 - PLAIN BEARING WITH IMPROVED WEAR RESISTANCE

EP4198327B1EP 4198327 B1EP4198327 B1EP 4198327B1EP-4198327-B1

Inventors

  • DZWONCZYK, JOANNA STEFANIA
  • Dennis, Grant James
  • Colton, Michael Brett

Dates

Publication Date
20260506
Application Date
20211220

Claims (5)

  1. Plain bearing comprising an outer ring (2) and an inner ring (3) each made of a metal material and comprising respectively an inner surface (2a) and an outer surface (3b) intended to cooperate with each other for the relative movement of the outer and inner rings (2, 3), characterized in that at least the outer surface (3a) of the inner ring (3) is provided with a plasma electrolytic oxidation coating and/or at least the inner surface (2a) of the outer ring (2) is provided with a plasma electrolytic oxidation coating, and wherein the metal material comprises an aluminum alloy, characterized in that the major alloying element of the aluminum alloy is copper, zinc, or a combination of magnesium and silicon.
  2. Plain bearing according to claim 1, further comprising a self-lubrification liner (5) interposed between the inner surface (2a) of the outer ring (2) and the outer surface (3b) of the inner ring (3).
  3. Plain bearing according to claim 2, wherein the self-lubricating liner (5) comprises a phenolic resin matrix filled with glass fibers.
  4. Plain bearing according to any of preceding claims, wherein the outer surface (3a) of the inner ring (3) is made of aluminum alloy having the outer surface (3a) coated with the plasma electrolytic oxidation coating and the outer ring (2) is made of an aluminum alloy material having the inner surface (2a) uncoated.
  5. Plain bearing according to any of preceding claims, wherein the inner surface (2a) of the outer ring is concave and the outer surface (3a) of the inner ring is convex.

Description

The present invention generally relates to plain bearings and more precisely, to improved wear resistance of plain bearings particularly suitable for aerospace applications as for example disclosed in CN 208 997 175 U. Typically, in self-lubricating plain bearings, hard materials such as steel, or hard coatings such as ceramics, are used coupled with a self-lubricating material. The combination results in an optimised wear and friction resistance at the interface between the inner ring and the outer ring of the plain bearing. The self-lubricating material usually consists in a liner and is considered as a consumable material, whereas the opposing counter-surface is optimised to have none or very low wear. In order to comply with weight reduction requirement in aerospace industry, heavy materials of plain bearings such as steel have been substituted by light alloys. Light alloys, however, have poor tribology properties, especially when used against a composite self-lubricating liner. For example, under very low loads, aluminum alloy exhibits abrasive wear after very few oscillating cycles. It is known to apply hard coatings by surface treatment method such as Physical Vapor Deposition (PVD) or High Velocity Oxy Fuel (HVOF) to enhance the lifetime of plain bearings made of steel, but also light alloys such as titanium. Nevertheless, coatings obtained by HVOF or PVD techniques cannot be applied to certain light alloys as a substrate, such as aluminum, since the high process temperatures of these methods would lead to overaging the material and lead to a reduction on mechanical properties. PVD and HVOF techniques being not suitable for aluminum light alloys, it is possible to form an electrochemically produced layer of aluminum oxide on the surface of aluminum alloy by hard anodising method. The resulting coating enables to improve the resistance to wear of the aluminum alloy. The downside of this solution is that the wear resistance of the coated aluminum alloy remains poor as compared with coated steels. Consequently, the present invention intends to overcome these disadvantages by providing a plain bearing having an improved wear resistance that can be obtained from light alloys such as aluminum having limited wear resistance properties. One object of the invention is to provide a plain bearing comprising an outer ring and an inner ring each made of a metal material and comprising respectively an inner surface and an outer surface intended to cooperate with each other for the relative movement of the outer and inner rings. According to the invention, at least the outer surface of the inner ring and/or at least the inner surface of the outer ring are provided with the plasma electrolytic oxidation coating and the metal material comprises an aluminium alloy, the major alloying element of the aluminum alloy being copper, zinc, or a combination of magnesium and silicon. Preferably, the plain bearing further comprises a self-lubrification liner interposed between the inner surface of the outer ring and the outer surface of the inner ring. In this case, the plain bearing is a self-lubricating plain bearing. More preferably, the self-lubricating liner may comprise a phenolic resin matrix filled with glass fibers. According to an embodiment, the outer surface of the inner ring may be made of aluminum alloy having the outer surface coated with a plasma electrolytic oxidation coating and the outer ring may be made of an aluminum alloy material having the inner surface uncoated. Advantageously, the plain bearing may be a spherical plain bearing. In this case, the inner surface of the outer ring is concave and the outer surface of the inner ring is convex. Advantageously, the plain bearing may be used in an aerospace application. A method of manufacturing a plain bearing according to the invention can comprise: providing an outer ring and an inner ring comprising respectively an inner surface and an outer surface intended to cooperate with each other for the relative movement of the outer and inner rings;forming a coating by plasma electrolytic oxidation process on the inner surface of the outer ring and/or on the outer surface of the inner ring; andassembling the outer ring and the inner ring. Other advantages and features of the invention will appear from the detailed description of embodiment of the invention, which are nonlimiting example, illustrated on the appended drawing of which: [Fig 1] illustrates a spherical plain bearing according to an embodiment of the invention. Referring to Figure 1, a spherical plain bearing 1 of main axis X comprises an outer ring 2 concentrically positioned with respect to an inner ring 3. The exemplified plain bearing 1 is a lightweight plain bearing for aerospace applications. The outer ring 2 has a concave bore or inner surface 2a of spherical shape, and the inner ring 3 has a convex outer surface 3a of spherical shape. The inner ring 3 also comprises a cylindrical bore 4. The inn