Brushless vibrator motor for a wireless silent alerting device

摘要

A dc brushless vibrator motor employs a cylindrical coreless stator winding unit having at least three stator coils arranged at about an even pitch angle and a rotor that includes an axially extended eccentrically-weighted permanent field magnet that is magnetized so as to have alternate north and south poles about the rotational axis of the rotor. A cross-section of the field magnet in a plane perpendicular to the rotational axis has generally an arcuate or sectorial shape which is within an angular range of 180 DEG to 270 DEG about the rotational axis. The center of mass of the rotor, therefore, is off the rotational axis, thereby causing vibrations.