Patent ID: 6700256
Filing Date: 2004-03-02
Classification: G11B,H02K

Abstract:
A brushless motor comprising:a rotor assembly which includes a substantially cylindrical rotor frame, a magnet that is concentrically disposed in the rotor frame to form a cylridrical spacing, and a shaft having one end fixed in a rotational center of the rotor frame; and a bearing for supporting the rotor assembly, wherein the rotor frame has a projected annular portion in a central portion thereof, the projected annular portion having a bore defining a small-bore portion and a large-bore portion which is spaced from an outer peripheral surface of the shaft, wherein an axial length L1 of the small-bore portion is in a range of DÃ—0.05&lE;L1&lE;DÃ—0.20 where D represents the diameter of the shaft.