US Patent 7884523 Brushless DC motor

A brushless DC motor includes a base, a stator, a rotor, and a leak flux absorber. The base couples with the rotor. The stator has a coil module and is mounted on the base. The rotor has a shaft and a permanent magnet, with the rotor coupling with the base through the shaft. A gap is axially formed between the permanent magnet and the coil module. Also, the leak flux absorber is disposed around the coil module and is adjacent to, partially in, or totally in the gap. Consequently, a leak flux generated by the permanent magnet, which does not pass through the coil module, is absorbed by the leak flux absorber and forms close magnetic flux paths, so that high-frequency noise in operation is thus lowered.