US Patent 7990002 Vibration motor

A vibration motor includes a rotary shaft, an armature core secured to the rotary shaft and having a plurality of salient poles, an armature coil wound around each of the salient poles except at least one salient pole, a frame serving as an outside cover, a plurality of magnets secured to the frame and having respective different polarities, and a weight adapted to rotate together with the rotary shaft and disposed eccentrically, wherein the weight is disposed inside the frame and secured to the armature core in such a manner that at least a part of the weight is inserted in a hollow provided in at least the one salient pole having no armature coil.