Belt pulley structure of engine

A belt pulley structure of an engine, comprising:

• a stepped portion formed in a shape that blocks a cavity in a radial direction, wherein the cavity is provided at a portion where a belt pulley and a torsional vibration damper face each other;
• an inertial ring coupled to the torsional vibration damper along a circumferential direction thereof;
• wherein the stepped portion is formed to be stepped at one surface of the inertial ring with a protruding shape that extends towards the belt pulley;
• a pulley decoupler coupled to the belt pulley;
• a damper rubber disposed on an inner side of the inertial ring;
• and
• a damper hub disposed on an inner side of the damper rubber, wherein the damper hub is directly coupled to the pulley decoupler;
• wherein the cavity generates resonance due to vibration of the engine and the pulley decoupler in a specific frequency band;
• and
• wherein sound waves generated by the cavity are blocked by the stepped portion.