Brushless dc motor

Abstract

A brushless DC motor provided with nine slots and eight poles includes a stator including a stator core having pole teeth on the outer circumference thereof and a coil wound around each pole tooth; a rotor disposed at an outside position of the outer circumference of the stator via a gap and having a multiply magnetized permanent magnet with plural magnetic poles; a pole tooth surface formed at a portion of the pole tooth and facing an inner circumference of the rotor; a recessed portion formed on the pole tooth surface; and a slot formed between the adjacent pole teeth and extending a first angular range around a rotational center of the rotor; in which the recessed portion extends in a second angular range around the rotational center of the rotor, the second angular range is 1.2 to 3.0 times the first angular range, the recessed portion has a radial depth which is 0.5% or more of an inner diameter of the permanent magnet, the pole tooth extends in a third angular range around a rotational center of the rotor, and the third angular range is 0.58 to 0.8 times a value which is obtained by dividing 360 degrees by the number of magnetic poles of the permanent magnet.

Dependencies are inferred from the claim text.