Development of Resin Overlay Bearing Material for Recent Automotive Engine 2017-01-0460
The number of vehicles with engines using idling stop systems and hybrid systems to improve fuel consumption has recently been increasing. However, with such systems the frequent starts and stops of the engine, where the oil film between the bearings and shaft is squeezed out and direct contact between the components is more likely, can result in increased wear of the engine bearings, particularly in the main bearing. Bearings with resin overlays have been shown to display superior resistance to wear from such start-stop cycles.
Moreover, cast iron shafts without quenching treatment have also been used in engines for cost reduction. Because the cast shaft has low hardness and unstable surface graphite after abrasive finishing, increase in the wear amount cannot be suppressed by conventional resin overlay in comparison with steel shaft. Therefore, the resin overlay with improved wear resistance achieved by adding hard particles was developed. However, the seizure resistance is reduced compared with the previous resin overly because resin overlays with hard particles don’t reform the oil film so readily due to their increased wear resistance.
From this background, a resin overlay with improved wear resistance achieved by adding hard particles, and also improved seizure resistance achieved by adding nanoparticles was developed. The resin overlay under development showed better wear and seizure resistance than conventional resin overlays in rig tests. We were able to obtain good results on engine tests and confirm the feasibility.