Essential Internal Combustion Engine Components

Engine Block

The engine block is the fundamental element where the cylinders are located. It features:

• Wear resistance in areas of contact with moving parts
• High mechanical resistance
• Structural rigidity
• Ability to quickly dissipate heat

Cylinder Head

The cylinder head's primary function is to tightly seal the top of the cylinder. This seal allows the piston to effectively compress air or an air-fuel mixture within the combustion chamber.

Oil Pan (Sump)

The oil pan, also known as the sump, closes the bottom of the engine block. Its crucial role is to act as a reservoir for engine oil. It is typically manufactured from a lightweight aluminum alloy.

Piston

The piston is located inside the cylinder, moving with a reciprocating motion. It is the element that seals the compression chamber, moving relative to the crankcase. The connecting rod is attached to the piston via a piston pin (or gudgeon pin), which allows for its movement and guidance. Key features of a piston include:

• Sufficient rigidity and mechanical resistance
• Good thermal conductivity
• Lightweight design (as light as possible)
• Consistent weight across all pistons to avoid dynamic imbalance
• Minimal thermal expansion (dilatation)

The shape of the piston head can be flat, concave, or convex, depending on engine design.

Piston Rings

Piston rings perform several vital functions:

• Ensuring the retention of combustion gases within the crankcase
• Providing proper lubrication of the piston to prevent oil from passing into the compression chamber
• Acting as support and a guide for the piston
• Serving as a medium through which residual combustion heat is transferred to the cylinder walls

Types of Piston Rings

Each ring has a specific role:

• First Ring (Fire Ring): Often called the "fire ring" due to its proximity to the combustion zone, this ring typically has a rectangular section. Its main role is to seal the combustion chamber.
• Second Ring: With similar features to the first, this ring complements the primary sealing function and controls the amount of oil remaining on the cylinder wall. It often has a trapezoidal section, which helps reduce the possibility of oil passing into the combustion chamber.
• Third Ring (Oil Control Ring): This ring is specifically designed for lubrication control. During the piston's descent, it scrapes excess oil from the cylinder walls, leaving just enough to ensure proper lubrication.

Piston Pin (Gudgeon Pin)

The piston pin, also known as a gudgeon pin, allows for oscillatory movement between the piston and the connecting rod, facilitating the transmission of force. There are three common types of piston pin mounting:

• Fixed to the piston, allowing the connecting rod to slide
• Fixed to the connecting rod, allowing the piston to slide
• Fully floating (allowing movement relative to both the piston and connecting rod)

Connecting Rod

The connecting rod is the crucial element that links the piston to the crankshaft. This union serves two main objectives:

• Transmitting the reciprocating movement of the piston to the rotary motion of the crankshaft
• Transferring the thrust force generated by combustion between these engine components

Connecting Rod Bearings

Connecting rod bearings have several critical functions:

• Ensuring smooth sliding between the connecting rod and crankshaft journal
• Cushioning the effects of high loads and impacts
• Preventing deterioration of the crankshaft's sliding surface