Patent ID: 7589444

Claim:
A brushless motor comprising: a stator unit disposed around a central axis; a rotor unit disposed in a rotatable manner relatively to the stator unit so as to rotate around the central axis; the rotor unit including a substantially cylindrical rotor magnet and a rotor holder having a cylindrical portion arranged to retain an outer circumferential portion of the rotor magnet; the stator unit including a stator core around which coils are wound and a circuit board on which circuit components defining a circuit to supply drive current to the coils are mounted; the circuit board including a position sensor arranged to sense a change in magnetic flux due to rotation of the rotor magnet; and the stator core includes teeth disposed at positions separated in the circumferential direction, each of which has an arm portion extending outward in the radial direction from the central axis, around which the coil is wound, and a stretching portion extending from the arm portion outward in the radial direction and in the circumferential direction on both sides; wherein the position sensor includes a sensor element that is positioned in the range within the lead angle of about four degrees or less in the circumferential direction from a reference line radially connecting the central axis and a point bisecting a line connecting neighboring stretching portions in the circumferential direction as a shortest distance, and within a distance of about one millimeter or less outward in the radial direction from an arc connecting outer edges of the neighboring stretching portions with respect to the central axis.