This is because the upper and lower bearings of the engine connecting rod bearings are made of different materials, and are mainly selected based on their working environment and load. The upper bearing is usually subjected to greater pressure and high temperature, so it requires better wear resistance and high temperature resistance; while the lower bearing is subjected to lighter loads and relatively less stringent requirements.
Copper upper bearing:
1. High temperature resistance: Copper has higher heat resistance and can maintain better strength and stability at high temperatures.
2. Good wear resistance: Copper material exhibits strong wear resistance when subjected to high pressure and friction, which can extend the service life of the engine.
3. Better lubricity: Copper has better lubricity, which helps reduce friction and wear.
Aluminum lower bearing:
1. Light weight: Aluminum material has a lower density, which can reduce the overall weight of the engine and improve fuel efficiency.
2. Good heat dissipation: Aluminum has strong thermal conductivity, which can dissipate heat more effectively and keep the engine temperature stable.
3. Lower cost: Aluminum is relatively more economical and suitable for parts that bear lighter loads.
Therefore, this design is to find a balance between performance, durability and cost.
