Patent ID: 6710563
Filing Date: 2004-03-23
Classification: G03B

Abstract:
A driving device comprising:a rotor having a cylindrical shape and having an outer peripheral surface and an inner peripheral surface, at least the outer peripheral surface being circumferentially divided into a plurality of sections magnetized so as to have alternately different poles, a coil arranged axially of said rotor and parallel thereto; at least one outer magnetic pole portion disposed to be magnetized by said coil, said outer magnetic pole portion formed so as to extend axially of said rotor, opposed to said rotor and arranged around said rotor such that an angle corresponding to a circumferential width of said outer magnetic pole portion opposed to said rotor about a rotational axis of the rotor is equal to a predetermined angle A; and an inner magnetic pole portion disposed to be magnetized by said coil, said inner magnetic pole portion having a hollow cylindrical shape opposed to the inner peripheral surface of said rotor; wherein the predetermined angle A is set to such a value that a rotational force acts on said rotor to return to a position in which a circumferential center of one of a plurality of magnetized sections on the outer peripheral surface of said rotor magnet is opposed to a circumferential center of said outer magnetic pole portion, when the circumferential center of one of a plurality of magnetized sections shifts from the position.