What is the function of the piston pin in an engine?

The function of the piston pin, also known as the wrist pin, is to hold the piston and connecting rod together. This pin serves a critical role in allowing the piston to pivot as it moves up and down within the cylinder, while simultaneously transferring the force generated from combustion to the connecting rod, which in turn drives the crankshaft. This connection is vital for the engine's operation, as it enables the conversion of linear motion of the piston into rotational motion at the crankshaft.

The other choices, while related to engine components, do not accurately describe the role of the piston pin. For instance, connecting the crankshaft to the flywheel pertains to the flywheel's function in maintaining engine inertia and smoothing out power delivery. Similarly, securing piston rings to the piston focuses on the sealing function needed for optimal combustion and engine efficiency, which is distinctly different from the role of the piston pin. Lastly, sealing off the crankcase from the combustion chamber is related to gaskets and seals within the engine, ensuring that combustion gases do not escape and that oil remains contained for lubrication. Therefore, the recognition of the piston pin's primary function in the assembly of the piston and connecting rod is essential to understanding engine mechanics.