Easily restarted brushless DC motor

Claim 1

A brushless motor comprising a stator core, a rotor having permanent magnets disposed around a rotor core of said rotor, a stator coil providing magnetic flux for exciting said rotor, a rotational position sensor for detecting a rotational position of said rotor, and a controller for controlling polarity of electrical power supplied to said stator coil in accordance with an output from said position sensor, wherein: (i) said stator core is made of a plurality of laminated electrical steel sheets, each of said electrical steel sheets having a substantially round aperture and being disposed around said aperture such that a closed magnetic circuit is formed around said aperture and such that a bore for receiving said rotor is formed by said aperture when said plurality of electrical steel sheets are laminated; (ii) said stator coil is composed of single coil with a pair of terminals, said stator coil being mounted on one side of said bore of the stator core; (iii) said rotational sensor is composed of a single magnetic, non-mechanical sensor which is disposed on said stator core adjacent to an outer surface of said rotor; (iv) the polarity of the electrical power of said stator coil is alternately switched over by said controller; and (v) said bore of said stator core has a shape such that a continual air gap is formed between a wall of said bore and an outer surface of said rotor, said air gap having portions containing a large gap and portions containing a small gap arranged alternately on a circumferential surface of said bore.