Patent ID: 8110956
Filing Date: 2012-02-07
Classification: H02K

Abstract:
1. A small motor having a quadrangular external shape in which a 4 -pole field magnet is attached to an inner peripheral surface of a motor casing made of metal, the motor comprising: a motor casing structure having a side wall formed into an overall shape of a quadrangle such that four flat side portions and arcuate corner portions equal in number to the four side portions and located at respective corners between the side portions are continuously joined together; and a field magnet structure having a circular inner peripheral surface having a diameter slightly greater than an outside diameter of a rotor and a quadrangular external shape, the quadrangular external shape being formed such that four flat side portions and arcuate corner portions equal in number to the four side portions and located at respective corners between the side portions are continuously joined together, wherein 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 a center of a motor shaft, and central angles of the arcuate corner portions fall within a range of 15 ° to 35 ° inclusive.