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The bearing is used for the sliding part of automotive parts, for example the brake pedal and the seat. As many of these bearings are aimed for maintenance free, the polymer based bearing that can be used under no lubrication is applied. This bearing material has three layer structures consisting of steel-backing and a porous copper alloy interlayer impregnated and covered with the polymer composite, which consists of poly-tetrafluoroethylene (PTFE), lead and others (1), (2). Lead has the characteristic to form the transferred film of PTFE to the countershaft, and this phenomenon improves the wear resistance. This bearing material shows the excellent bearing performance by the characteristic of lead under no lubrication. However, because lead has been designated as one of the environmental pollutants, the addition to the bearing material is being restricted in recent years. Therefore, lead free polymer based bearing that can be used under no lubrication was developed in this study.

Recently, exhaust emission has been enforced on diesel engines for the countermeasure of environmental problems. Accordingly, the cylinder pressure in the engine is being increased to improve fuel efficiency, the engine bearings must be used under severe conditions of high specific load. Because the connecting rod bearings, particularly of diesel engines, are used at high specific loads that exceed 100 MPa, elastic deformation of the bearing surface occurs, and the oil film thickness decreases at the edges of the bearing length in the axial direction. This causes the bearings to contact with the crankshaft, thus resulting in the wear of the bearings, which could even result in seizure. The following factors contribute to seizure: bearing materials, bearing shapes, machining methods, and incorrect assembly. Focusing on these factors, this study evaluated the behaviors exhibited by connecting rod bearings in actual engines by using the rig testers.

Recently, as for the rod guide bush bearing materials for shock absorbers, lower friction and the improvement of durability are required along with ride quality and longer life of automobile. Usually, lead is contained in bearing materials. However, the addition of the lead in bearing material is being restricted from the earth environmental problem. Bearing materials for shock absorbers are composite material consists of steel backing and covered with polymer surface layer. This basic material structure hasn't been changed till now, though it has been improved by changing its components and compositions based on the customer's requirement. Bearing material with both lower friction and excellent wear resistance has been developed in this study.