# Crankshaft’s function and Structure

The crankshaft is a high-speed rotating long shaft in the engine, which turns the linear reciprocating motion of the piston into rotational motion, and then transmits torque to the drive train of the chassis through the flywheel, and also drives the valve train and other auxiliary devices, so its The force conditions are quite complex. In addition to the centrifugal force of the rotating mass, it also bears the combined action of the periodically changing gas pressure and the reciprocating inertial force, so that the curved bearing is subjected to bending and torsional loads. In order to ensure reliable operation, the crankshaft must have sufficient strength and rigidity, and each working surface must be wear-resistant. And well lubricated.

Its structure is shown in the left side picture mainly composed of the main journal, connecting rod journal, oil seal journal, gear journal, pulley journal and crank arm, etc.