Patent ID: 7417347

Claim:
A skeleton type BLDC motor, comprising: a rotor having an elliptic-cylindrical shape, comprising an elliptic-cylindrically-shaped magnet having a north pole and a south pole separated by a separation plane and a magnet frame fixed to an inner circumferential surface of the magnet, wherein a rotary shaft is fixed to a center of the magnet frame and a diameter of the rotor at points where the separation plane intersects an outer circumference of the rotor is smaller than a diameter of the rotor at all other points along the outer circumference of the rotor to minimize resonance noise resulting from a higher degree of cogging torque; and a stator in which the rotor is disposed, comprising a first pole shoe and a second pole shoe, a pair of detent grooves being formed in an inner surface of the stator, wherein a diameter of the rotor at points where a plane perpendicular to the separation plane intersects the outer circumference of the rotor is greater than the diameter of the rotor at all other points along the outer circumference of the rotor, and the diameter of the rotor at the points where the plane perpendicular to the separation plane intersects the outer circumference of the rotor is approximately 1 millimeter to 1.5 millimeters greater than the diameter of the rotor at the points where the separation plane intersects the outer circumference of the rotor.