Vibrator motor for a wireless silent alerting device

摘要

A dc vibrator motor has a generally cylindrically-shaped magnetically conductive case, a ring-shaped permanent field magnet, and an armature rotor including a shaft. The field magnet has at least four and at most eight alternate north and south pole sections arranged at an even angular pitch coaxially with the shaft. The armature rotor has at least three armature poles having an angular interval of 60 DEG between adjacent poles and at most six armature poles having an angular interval of 30 DEG between any pair of adjacent poles and at least six and at most twelve commutator segments arranged at an even angular pitch coaxially with the shaft. A pair of commutator brushes have an angular interval of at least 45 DEG and at most 90 DEG . Since all of the armature poles are situated within an angular range of 180 DEG about the shaft, the center of mass of the rotor is radially off the shaft, thereby causing vibrations.