Knowledge of Engine Piston Parts

    The piston is a key component of the excavator engine. It bears gas pressure and transmits it to the connecting rod via the piston pin to drive the crankshaft to rotate. The piston crown also forms part of the combustion chamber.

    The piston-connecting rod assembly includes the piston, piston rings, piston pin, connecting rod, and connecting rod bearings.

Operating Conditions:

The piston operates under high temperature, high pressure, high speed, and poor lubrication.

1. It contacts high-temperature gas directly, with instantaneous temperature over 2500K; piston crown reaches 600–700K with uneven temperature distribution.

2. It bears high gas pressure, especially during the power stroke: 3–5MPa for gasoline engines, 6–9MPa for diesel engines, causing impact and side pressure.

3. It reciprocates at 8–12m/s with changing speed, generating large inertia force and extra load. Under such severe conditions, the piston may deform, wear faster, suffer extra load and thermal stress, and corrode from gas.

Requirements:

1. Sufficient rigidity and strength for reliable force transmission.

2. Good thermal conductivity, high pressure resistance, high temperature resistance, and wear resistance.

3. Light weight to minimize reciprocating inertia. High-strength aluminum alloy is commonly used. High-grade cast iron or heat-resistant steel is used for some low-speed diesel engines.