Patent ID: 7476076

Claim:
A centrifugal fan comprising: a scroll casing that has first and second flat base walls, a circumferential side wall covering the circumferences of said base walls, an air inlet that is opened in an axial direction being formed on a center portion of said first base wall and an exhaust port that is opened in a circumferential direction being formed on one portion of said circumferential side wall; a motor that is attached to a center portion of said second base wall at the inside of said casing so that a rotating shaft of the motor is perpendicular to said second base wall; an impeller that is fixed to said rotating shaft, the impeller having many blades along the outer region thereof; and an airflow correction mechanism that forms smooth airflow when said impeller rotates, wherein said airflow correction mechanism has an annular rib that is formed on the inside surface of said first base wall so as to be jutted to the side of said second base wall and to be concentric with said rotating shaft, and a recess portion that is formed on every blade of said impeller so that said annular rib is inserted therein with a predetermined gap, said annular rib and said recess portion being configured to change the direction of airflow directed to said air inlet back to a space between said blades, and wherein said annular rib is substantially perpendicular to said first base wall and is at the outer region of said air inlet, an outer bottom portion of said annular rib having a circular curve section so that the outer circumferential surface of said annular rib is smoothly connected to the inside surface of said first base wall, and an inner tip portion of said annular rib having a circular curve section.