Patent ID: 8408884

Claim:
A fan, comprising: an airflow guiding structure whose an outer radius increases gradually from a top of the airflow guiding structure to a bottom of the airflow guiding structure; an impeller disposed on the airflow guiding structure and the impeller comprising a hub and a plurality of blades disposed around the hub; a motor disposed in the hub; a circuit board for driving the motor, wherein the circuit board and at least a portion of the motor are disposed in an accommodating space formed inside the airflow guiding structure; and a guiding ring connected to a module housing or connected to the airflow guiding structure via at least one connecting element, wherein a predetermined distance is arranged between an inner surface of the guiding ring and outer edges of the blades, an inlet is formed at a top of the guiding ring, an outlet is formed between a bottom of the guiding ring and an outer surface of a sidewall of the airflow guiding structure, a first predetermined distance is defined between the top of the guiding ring and a top of the blades, and a ratio of the first predetermined distance to the length of a conjunction of the blades and the hub ranges from 0.3 to 1; wherein when the impeller rotates, an airflow enters the fan from the inlet and flows along the outer surface of the sidewall of the airflow guiding structure, then the airflow exits the fan through the outlet, and a direction of the airflow passing through the outlet is different from a direction of the airflow passing through the inlet.