Patent ID: 7714472
Filing Date: 2010-05-11
Classification: H02K

Abstract:
1. A small DC motor, comprising: a motor frame having two ends and a side wall; wherein the side wall surrounds a magnet and includes four straight portions and at least four connecting portions; wherein each of the connecting portions is located between adjacent two of the four straight portions; wherein the magnet includes at least four poles and has an outer surface conforming to the motor frame and an inner surface forming a circular opening and wherein the width of the magnet between the inner and outer surface varies; a rotor rotatably disposed in the circular opening, wherein the side wall includes the same number of connecting portions as the number of poles contained in the magnet and wherein each of the connecting portions is a segment of a circle having a center located away from the center of the circular opening and having a radius less than the radius of the circular opening so that the ratio of the radius of the connecting portion to the radius of the circular opening is between about 65 percent to about 85; and wherein an air gap provided between the inner surface of the magnet and the rotor has a constant distance.