What kind of bearings are commonly used in automobile engine crankshafts?

Automotive engine crankshafts primarily utilize precision sliding bearings as support components, designed specifically for the specific operating conditions of the engine. Crankshaft bearings are primarily classified into two categories:

1. Main bearings (main bearing shells)

These bearings are mounted on the main bearing housing of the engine block and support the crankshaft's main journal. Modern engine main bearings typically utilize a multi-layer composite structure: a steel backing plate provides strength, an intermediate layer is an anti-friction alloy (commonly a copper-lead alloy or an aluminum-based alloy), and the surface is coated with an extremely thin, wear-resistant coating (such as babbitt or polymer coating).

2. Connecting rod bearings (connecting rod shells)

Connecting the connecting rod to the crankshaft, the connecting rod journal must withstand even greater explosive pressure. Connecting rod bearings in high-performance engines typically utilize a three-layer composite structure: a steel backing plate, a copper-lead alloy transition layer, and a 0.02mm thick tin or indium coating. This design ensures both load-bearing strength and excellent fatigue resistance and emergency operation capabilities.

Key reasons for choosing sliding bearings:

Superior load capacity (withstands burst pressures exceeding 200 MPa)

Improved vibration absorption and noise reduction

More compact design

Longer service life (over 200,000 kilometers with proper maintenance)

These precision bearings require strictly controlled clearances during assembly (typically 0.02-0.05 mm) and rely on the oil film formed by the engine oil for lubrication. Their performance directly impacts the engine's power output and reliability.