Abstract: A worm wheel (50) is structured integrally with an output shaft (52). The worm wheel (50) includes the output shaft (52), a circular flange (50a) with the output shaft (52) placed as the center, and teeth (50b) formed on the periphery of the flange (50a) and in mesh with a worm. The flange (50a) is provided with a first recessed flange portion (50c) opposite to the side of the output shaft (52), and the bottom (54) of the first recessed flange portion (50c) has a ring-shaped first planar portion (54a).

Abstract: A worm wheel (50) is structured integrally with an output shaft (52). The worm wheel (50) includes the output shaft (52), a circular flange (50a) with the output shaft (52) placed as the center, and teeth (50b) formed on the periphery of the flange (50a) and in mesh with a worm. The flange (50a) is provided with a first recessed flange portion (50c) opposite to the side of the output shaft (52), and the bottom (54) of the first recessed flange portion (50c) has a ring-shaped first planar portion (54a).

Abstract: Magnetic poles are arranged such that the N pole and the S pole alternate in a circumferential direction. Two N poles face each other with an interval of 180° therebetween, and two S poles face each other with an interval of 180° therebetween. Each of the magnetization center of a North magnetic pole and the magnetization center of a South magnetic pole is positionally shifted from the center position between the magnetization centers of two magnetic poles of the other polarity located on opposite sides of the North or South magnetic pole. The magnetization centers of the magnetic poles are disposed in such a manner as to be positionally shifted from geometric centerlines. Brushes are disposed along the respective geometric centerlines. The magnetization centers of two adjacent magnetic poles are positionally shifted toward or away from each other by the same shift angle ? with respect to the respective geometric centerlines.

Abstract: The side wall of a motor casing is formed into a quadrangular shape such that four flat side portions, and arcuate corner portions located at respective corners are continuously joined together. A field magnet having a quadrangular external shape is formed such that four flat side portions, and four arcuate corner portions located at respective corners are continuously joined together. The arcuate corner portions of the motor casing and the arcuate corner portions of the field magnet extend along respective circles having a center located at the center of a motor shaft, and the central angles of the arcuate corner portions fall within a range of 15° to 35° inclusive. The field magnet is press-fitted or bonded into the motor casing such that the corner portions of the field magnet come into close contact with the corner portions of the motor casing.

Abstract: Magnetic poles are arranged such that the N pole and the S pole alternate in a circumferential direction. Two N poles face each other with an interval of 180° therebetween, and two S poles face each other with an interval of 180° therebetween. Each of the magnetization center of a North magnetic pole and the magnetization center of a South magnetic pole is positionally shifted from the center position between the magnetization centers of two magnetic poles of the other polarity located on opposite sides of the North or South magnetic pole. The magnetization centers of the magnetic poles are disposed in such a manner as to be positionally shifted from geometric centerlines. Brushes are disposed along the respective geometric centerlines. The magnetization centers of two adjacent magnetic poles are positionally shifted toward or away from each other by the same shift angle ? with respect to the respective geometric centerlines.

Abstract: The side wall of a motor casing is formed into a quadrangular shape such that four flat side portions, and arcuate corner portions located at respective corners are continuously joined together. A field magnet having a quadrangular external shape is formed such that four flat side portions, and four arcuate corner portions located at respective corners are continuously joined together. The arcuate corner portions of the motor casing and the arcuate corner portions of the field magnet extend along respective circles having a center located at the center of a motor shaft, and the central angles of the arcuate corner portions fall within a range of 15° to 35° inclusive. The field magnet is press-fitted or bonded into the motor casing such that the corner portions of the field magnet come into close contact with the corner portions of the motor casing.

Abstract: A small-sized motor having a polygonal outer shape includes four or more field magnets attached to the inner surface of a motor casing made of metal. A tubular portion of the motor casing is formed into a polygonal tubular shape such that flat side portions equal in number to field poles, and flat or curved corner portions equal in number to the field poles and each being located between the adjacent side portions are sequentially joined together. The field magnets have a smaller thickness at portions corresponding to the side portions of the motor casing and a larger thickness at portions corresponding to the corner portions of the motor casing. The field magnets are fixed while coinciding in center position with the corresponding corner portions of the motor casing and while being pressed against the corresponding corner portions of the motor casing from inside.

Abstract: A small-sized motor having a polygonal outer shape includes four or more field magnets attached to the inner surface of a motor casing made of metal. A tubular portion of the motor casing is formed into a polygonal tubular shape such that flat side portions equal in number to field poles, and flat or curved corner portions equal in number to the field poles and each being located between the adjacent side portions are sequentially joined together. The field magnets have a smaller thickness at portions corresponding to the side portions of the motor casing and a larger thickness at portions corresponding to the corner portions of the motor casing. The field magnets are fixed while coinciding in center position with the corresponding corner portions of the motor casing and while being pressed against the corresponding corner portions of the motor casing from inside.

Abstract: A permanent magnet field-type compact DC motor having a high output and a low cogging torque is made by fixing a pair of rare earth magnets mainly composed of rare earth-iron-based rapidly quenched and solidified flakes to a soft magnetic frame so as to extend along an inner peripheral surface thereof, and by unsaturation-magnetizing the rare earth magnets so that demagnetization curves at circumferentially opposite end portions of the rare earth magnets are made smaller than a demagnetization curve at a central portion of a magnetic pole of each of the rare earth magnets.