Patent ID: 7766627

Claim:
A motor device for a fan comprising: a fan base having a central barrel extending therefrom, the barrel having an inner circumferential side and an outer circumferential side and the inner circumferential side fitting with a plurality of ball bearings; an impeller set further comprising an impeller, a shaft, a spring, a motor case and a magnet, wherein the shaft has two ends with one of the ends being attached to the center of the impeller and another one of the ends passing through the bearings, the spring is disposed between one of the bearings and the center of the impeller and surrounds the shaft, the motor case is disposed inside the impeller and the magnet is disposed inside the motor case; and a motor set further comprising an insulation frame being joined to the outer circumferential side, a silicone sheet set being mounted to a middle area of the insulation frame, a coil being wound to the insulation frame and a circuit board being disposed between the insulation frame and the fan base; characterized in that barrel has an annular deep groove between the inner circumferential side and the outer circumferential side for a stop ring being attached to an inner wall surface of the groove to reinforce the outer circumferential side so as to prevent the barrel from deforming due to bending and prevent the motor set from displacing eccentrically or loosening off.