06/08/2025
📌 Anatomy of a Piston Assembly: Breakdown of Key Engine Parts and Their Functions:
A piston assembly in an internal combustion engine is a critical component responsible for converting combustion energy into mechanical motion.
Here’s a breakdown of its main parts:
1. Piston:
The piston is a cylindrical component that moves up and down inside the engine cylinder. Made from lightweight aluminum alloy, it transfers the force from combustion to the crankshaft via the connecting rod.
2. Compression Rings:
These are located in grooves near the top of the piston. They form a seal between the piston and cylinder wall, preventing combustion gases from escaping into the crankcase and maintaining compression pressure.
3. Oil Rings:
Situated below the compression rings, oil rings control the amount of lubricating oil on the cylinder walls. They scrape off excess oil and return it to the sump, preventing oil from entering the combustion chamber.
4. Gudgeon Pin (Wrist Pin):
This hollow cylindrical pin connects the piston to the small end of the connecting rod, allowing for pivoting motion as the piston moves up and down.
5. Circlip:
Circlips are snap rings placed in grooves at the ends of the gudgeon pin hole. They prevent the gudgeon pin from sliding out of position during engine operation.
6. Bushing:
Found in the small end of the connecting rod, the bushing is a sleeve bearing that reduces friction between the connecting rod and gudgeon pin.
7. Connecting Rod:
This rod links the piston to the crankshaft. It converts the piston's linear motion into the rotary motion of the crankshaft. It experiences both compression and tension forces during engine cycles.
8. Bearing Shells:
These are thin metal liners located at the big end of the connecting rod. They provide a low-friction surface between the connecting rod and crankshaft, absorbing wear and supporting smooth rotation.
9. Cap:
The cap is the detachable part of the connecting rod's big end. It holds the bearing shells and bolts onto the crankshaft journal, securing the connection.
