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With increased awareness of environmental issues and regulations, developments for recent automotive engines are progressing towards engines with low fuel consumption. Due to these changes, automotive engine bearings are increasingly used in harsher environments, with higher loading and corresponding wear. From this background, resin overlays, where solid lubricant is dispersed in a resin binder, are being developed. Resin overlays show excellent sliding properties under boundary lubrication conditions, and are known to have superior wear and fatigue resistance compared with conventional aluminium based bearings. However, while conventional resin overlay bearings display excellent sliding properties, they tend to have inferior seizure resistance compared to Al-Sn-Si alloy bearings. In this study, by optimizing the strength of the resin overlay layer with addition of calcium carbonate particles, a resin overlay with equal wear resistance but improved seizure resistance was developed.

Recently, a Lead-free aluminum alloy bearing with available fatigue strength is partially applied for plain bearings in automotive engines as replacement of a conventional copper alloy bearing with lead based overlay, according to requirement of ELV regulation, which requires the lead removal from bearing. However, our recent investigation made clear that the aluminum alloy bearing did not have enough running-in property when operated under severe condition of thinner oil film in recent automotive engine with further higher performance. Based upon these backgrounds, a lead-free bearing was newly developed by applying overlay onto the aluminum alloy bearing for better running-in property of the bearing.