Method of manufacture a sliding bearing

Abstract

A method of manufacturing a sliding bearing comprising providing a substrate as a cathode in an electrolyte within which a hard particulate is suspended, and depositing a composite layer of hard particulate embedded in a metallic matrix by applying a repeating cycle of bias pulses to the substrate wherein each cycle comprises a high cathodic bias portion and a further bias portion selected from the group consisting of a low cathodic bias portion, a zero cathodic bias portion and an anodic bias portion, and a sliding bearing manufactured by such a method.

Description

[0001]The present invention relates to a method of electroplating a sliding bearing with a composite layer of hard particulate incorporated in a metallic matrix, and more particularly, but not exclusively, to bearing shells and thrust washers.BACKGROUND[0002]Bearing shells for journaled engine bearings typically comprises a strong steel backing layer, a lining layer and an overlay layer that provides the running surface for the journaled shaft, e.g. a hollow generally semi-cylindrical steel backing layer, a copper-based alloy lining layer, and a tin, tin-based alloy or composite overlay layer on the inner surface.[0003]It is desirable to provide increased wear resistance and to improve the fatigue strength of layers in bearing linings, particularly overlay layers. A particular challenge to bearing overlay layer performance is provided by the configuration of vehicle engines to save fuel by using a stop-start operation, in which the engine is stopped each time the vehicle stops, in c...

AI Technical Summary

Problems solved by technology

A particular challenge to bearing overlay layer performance is provided by the configuration of vehicle engines to save fuel by using a stop-start operation, in which the engine is stopped each time the vehicle stops, in contrast to conventional engine operation, in which the engine is kept running throughout a vehicle's journey.

The particular problem that an engine configured for stop-start operation presents arises because engine bearings are conventionally hydrodynamically lubricated, with little or no lubrication initially being provided to the bearings when the engine starts, leading to particularly significant wear during the start-up phase.

However, the production of such composite layers, with a high concentration of hard particulate, is difficult by conventional electroplating techniques, particularly in a tin-based alloy matrix (e.g. at least 50% wt tin), and most particularly in the case of a pure tin matrix.

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