Cooling fan

摘要

A cooling fan includes a frame (100) and an impeller (200) having a plurality of blades (240) disposed in the frame (100). The frame (100) has a cap (120) with an air inlet (122), a base (140) and a sidewall (160) extending from a periphery of the base (140) with an air outlet (180) defined therein. The cap (120) is mounted on the sidewall (160) with a chamber formed between the cap (120), the base (140) and the sidewall (160). A curved tongue portion (190) is formed on the sidewall (160) in vicinity of the air outlet (180). A protrusion (124) is formed on the cap (120) in vicinity of the curved tongue portion (190) and protrudes into the air inlet (122).