Patent ID: 7768157

Claim:
A brushless motor operable in a given drive direction, comprising: a first member including one or more first permanent magnets magnetized in a direction perpendicular to the drive direction such that the one or more first permanent magnets have identical polarity; a second member opposing the first member and including an electromagnetic coil wound in a direction parallel to the drive direction; a drive control circuit configured to supply electric power to the electromagnetic coil; and a driving force prevention member that prevents occurrence of driving force through electromagnetic interaction between a part of the electromagnetic coil and the first permanent magnet, wherein the drive control circuit supplies a drive current in a given first electric current direction to the electromagnetic coil without changing the electric current direction to operate the brushless motor in the drive direction; the electromagnetic coil has a first coil portion facing the first permanent magnet, and a second coil portion farther from the first permanent magnet than the first coil portion, the driving force prevention member allows electromagnetic interaction between the first coil portion and the first permanent magnet while preventing electromagnetic interaction between the second coil portion and the first permanent magnet, the driving force prevention member is a second permanent magnet installed on an opposite side of the first permanent magnet with regard to the second drive element, the second permanent magnet is arranged so that same poles of the first and second permanent magnets are mutually opposing, the electromagnetic coil has as a core member a magnet assembly which includes a magnetic material member and two permanent magnets installed on both sides of the magnetic material member such that same poles of the two permanent magnets are respectively attracted by the magnetic material member, and the two permanent magnets of the magnet assembly are arranged opposite to the first and second permanent magnets respectively such that different poles are mutually opposing.