COOLING FAN

PURPOSE: A cooling fan is provided to change the RPM(Revolutions Per Minute) of a fan slowly and to reduce production costs. CONSTITUTION: A cooling fan includes: a case(10); a mounting plate(20) fixed inside the case; a rotatable shaft(30) having an end supported to the case and the other end mounted on the mounting plate rotatably; a ring gear(41) integrally rotated with the rotatable shaft; a pinion gear(42) mounted in the perpendicular direction of the ring gear; plural blades(50) fixed to the center of the pinion gear and radially mounted on the case; and a coil member(60) mounted at the rotatable shaft protruded outside the case. The rotatable shaft and the ring gear are integrally rotated when the coil member is expanded according to the temperature of external air. The plural blades have angles changed according to a rotational angle of the rotatable shaft. Thereby, H-Q(Head-Quantity) characteristics of the cooling fan are changed. The coil member is slowly changed according to the temperature of air at the rear of a radiator. The cooling fan has slowly strokes changing according to the temperature of air. Therefore, the cooling fan changes the flow of air without a fan clutch.