Brushless DC motor

Abstract

An optimum arrangement of position detectors which is inexpensive but hardly affected by intrinsic mechanical deflection or radial displacement on a rotary structure or motor and by a secondary artifact or variation i the magnetic coupling resulting from the mechanical deflection or radial displacement. A brushless DC motor with N phases (N≧2) according to the present invention is provided having position detectors of which signal outputs are indicative of the location of magnetic poles of a rotor and used for controlling the rotation for a constant speed. More particularly, it includes any two adjacent position detectors being spaced from each other by a spatial angle θi (rad) about the center of the rotor, (1/n)*(θi/2π)<KM is established where i=1 to N−1, 0<θi<2π/N, KM is the mechanical time constant of the motor (sec), and n is the number of revolutions (rps). Since the position detectors of different phases are spatially gathered in a small region, the magnetic imbalance resulting from mechanical deflection or radial displacement is attenuated. As the result, a variation of the Hall voltage output of each position detector due to the magnetic unbalance will be minimized.

Dependencies are inferred from the claim text.